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Opheline kinase (OK) is one of the phosphagen kinases (PKs) restricted to annelids, but the amino acid sequence has not been determined yet. The OK enzyme was isolated in 1966 from the polychaete Ophelia neglecta (Opheliidae) and shown to have somewhat broader activities for the various substrates opheline, lombricine and taurocyamine. To determine the OK sequence, we analyzed the RNA sequencing data for Ophelina sp. and Thoracophelia sp., belonging to Opheliidae. Four PK sequences, namely, taurocyamine kinase (TK), creatine kinase (CK), mitochondrial CK (MiCK) and putative OK, were identified in both species, and the recombinant Ophelina enzymes were expressed in E. coli and purified. Since the substrate opheline was not commercially available, we used the partial activity toward taurocyamine to infer the enzyme specificity. The putative Ophelina OK showed lower activity to taurocyamine with a Vmax/Km nearly identical to a previously published value for an OK from a related species Ophelia neglecta. Under the same conditions, the true Ophelina TK showed much higher activity. Thus, the putative Ophelina enzyme was determined to be OK. The amino acid sequence alignment indicated that Ophelina and Thoracophelia OKs have five amino acid deletions in the GS region, like those of LKs and AKs, and the guanidino substrate specific residue was Lys, the same as LKs. In the phylogenetic tree constructed from annelid PK amino acid sequences, the OK sequences formed a distinct cluster, and it was placed near the TK and lombricine kinase (LK) clusters. This is the first report of the amino acid sequence for the OK enzyme.

Soil environment contaminated by Escherichia coli O157:H7 which come from the waste of infected animals. Earthworms can live in the pathogens-polluted soil by their innate immunity. How the proteins of earthworms E. fetida will response to E. coli O157:H7-contaminated-soil still unclear? To identify the defense proteins under E. coli O157:H7 stress, we performed a proteomic analysis of earthworm under E. coli O157:H7 exposure through an iTRAQ technology. In total, we found 283 non-redundant proteins, including fibrinolytic protease 1, lombricine kinase, lysozyme, gelsolin, coelomic cytolytic factor-1, antimicrobial peptide lumbricin-l, lysenin, and et al. The proteins participate in metabolic processes, transcription, defense response to bacterium, translation, response to stress, and transport. The study will contribute to understand why earthworm can live in the pathogens-polluted environment.

Phosphagen kinases (PKs) play major roles in the regulation of energy metabolism in animals. Creatine kinase (CK) is the sole PK in vertebrates, whereas several PKs are present in invertebrates. We previously identified a contiguous dimer taurocyamine kinase (TK) from the trematode Schistosoma japonicum (Sj), a causative agent of schistosomiasis. SjTK contiguous dimer is comprised of domain 1 (D1) and domain 2 (D2). In this study, we used SjTK contiguous dimer (SjTKD1D2) or truncated single-domain constructs (SjTKD1 or SjTKD2) and employed site-directed mutagenesis to investigate the enzymatic properties of TK mutants. Mutation in SjTKD1 or SjTKD2 (D1E222G or D2E225G) caused complete loss of activity for the substrate taurocyamine. Likewise, a double mutant (D1E222GD2E225G) in the contiguous dimer (D1D2) exhibited complete loss of activity for the substrate taurocyamine. However, catalytic activity in the contiguous dimer remained in both of D1 inactive mutant (D1D2D1E222G) and D2 inactive mutant (D1D2D2E225G), suggesting that efficient catalysis of SjTKD1D2 is dependent on the activity of D1 and D2. The catalytic efficiency of the mixture of both single domains (WTD1 + WTD2) showed same enzymatic properties ( K m Tauro = 0.68; V max / K m Tauro = 137.04) to WTD1D2 ( K m Tauro = 0.47; V max / K m Tauro = 144.30). This result suggests that the contiguous dimeric structure is not essential for the catalytic efficiencies of both domains of SjTK. V max / K m Tauro of the mixture of wild-type and inactivated domains (78.02 in WTD1 + D2E225G and 128.24 in D1E222G + WTD2) were higher than the corresponding mutants (47.25 in D1D2D1E222G and 46.77 in D1D2D2E225G). To identify amino acid residues that are critical for taurocyamine binding, we performed alanine scanning mutagenesis at positions 57–63 on the guanidino specificity (GS) region of the SjTKD1, which is considered to be involved in guanidino-substrate recognition. R63A and R63Y mutants lost activity for taurocyamine, suggesting that these residues are associated with taurocyamine binding. In addition, we investigated the role of Tyr84 in D1 and found an association with substrate alignment. The Y84 residue was replaced with R, H, K, I, A, and G. Although the activities of each mutant were decreased ( V max = 2.36–67.50 μmol Pi/min/mg protein), Y84 mutants possess binding affinity for taurocyamine ( K m Tauro = 3.19–10.04 mM). The D1Y84R, D1Y84H, D1Y84K, and D1Y84A mutants exhibited low activity for taurocyamine, whereas the D1Y84I and D1Y84G mutants exhibited slightly decreased activity compared with the other Y84 mutants. The D1Y84K mutant lost substrate synergy between taurocyamine and ATP, suggesting that this mutation moves the position of the GS loop, similar to that of lombricine kinase (LK), and interferes with taurocyamine binding. This is the first comprehensive investigation of essential amino acid residues for substrate catalysis in trematode TK.

Lombricine kinase is an annelid enzyme that belongs to the phosphagen kinase family of which creatine kinase and arginine kinase are the typical representatives. The enzymes play important roles in the cellular energy metabolism of animals. Biochemical, physiological and molecular information with respect to lombricine kinase is limited compared to other phosphagen kinases. This study presents data on the cDNA sequences of lombricine kinase from two smaller oligochaetes, Enchytraeus sp. and Stylaria sp. The deduced amino acid sequences are analyzed and compared with other selected phosphagen kinases. The intron/exon structure of the lombricine kinase gene was determined for these two species as well as two additional oligochaetes, Lumbriculus variegatus and Tubifex tubifex, and compared with available data for annelid phosphagen kinases. The data indicate the existence of a variable organization of the proposed 8-intron/9-exon gene structure. The results provide further insights in the evolution and position of these enzymes within the phosphagen kinase family.

The molecular mechanisms underlying innate immunity in the earthworm E. fetida remain unclear. For the recognition of innate immunity in the earthworm E. fetida, a detailed knowledge of this proteome is a prerequisite. The absence of a high-resolution E. fetida proteome map prompted us to determine E. fetida protein spots that can be visualised on 2-D protein gels. In this study, we present a preliminary description of the whole earthworm E. fetida proteome. A highly detailed two-dimensional gel electrophoresis (2-DE) map of the E. fetida proteome was established and approximately 1500 protein spots were detected from the earthworm sample when applying a 500 μg protein 2-DE in the pH range 3.0 - 10.0. We present a 2-DE proteome map of E. fetida, identifying 76 different proteins by matrix-assisted laser desorption/ionization-tandem time of flight mass spectrometry (MALDI-TOF/ TOF-MS) analysis. These identified proteins, including heat shock protein 90 (Hsp90), chaperonine protein HSP60, caspase-8, fibrinolytic protease 0, gelsolin-like protein, lombricine kinase, coelomic cytolytic factor1 (CCF 1), manganous superoxide dismutase (MnSOD), triosephosphate isomerase, extracellular globin-4, lysenin, and intermediate filament protein, glyceraldehyde-3- phosphate dehydrogenase, et al., are involved in several processes, including transcripttion, translation, the tricarboxylic acid cycle, the cellular amino acid metabolic process, protein amino acid phosphorylation, glycolysis, and the glucose metabolic process. These 2-DE data will enhance future comparisons of immunity, toxicology, biotic processes and other challenges, thereby allowing for further study of the molecular mechanisms in response to environmental stressors, and it will be useful to investigate environmental proteomics in invertebrate earthworms.

Lombricine kinase is a member of the phosphagen kinase family and a homolog of creatine and arginine kinases, enzymes responsible for buffering cellular ATP levels. Structures of lombricine kinase from the marine worm Urechis caupo were determined by x-ray crystallography. One form was crystallized as a nucleotide complex, and the other was substrate-free. The two structures are similar to each other and more similar to the substrate-free forms of homologs than to the substrate-bound forms of the other phosphagen kinases. Active site specificity loop 309–317, which is disordered in substrate-free structures of homologs and is known from the NMR of arginine kinase to be inherently dynamic, is resolved in both lombricine kinase structures, providing an improved basis for understanding the loop dynamics. Phosphagen kinases undergo a segmented closing on substrate binding, but the lombricine kinase ADP complex is in the open form more typical of substrate-free homologs. Through a comparison with prior complexes of intermediate structure, a correlation was revealed between the overall enzyme conformation and the substrate interactions of His178. Comparative modeling provides a rationale for the more relaxed specificity of these kinases, of which the natural substrates are among the largest of the phosphagen substrates.

Identification of differential proteomic responses to cadmium (Cd) would provide a means for better understanding the survival mechanisms of the earthworm, Eisenia fetida, living in a Cd-polluted environment, and the stress responses can be assessed by ecotoxiptoromics approaches. Extracts of whole earthworm collected at days 7, 14, 21, and 28 after Cd exposure were analyzed by 2-DE and quantitative image analysis. In total, 143 proteins demonstrated significant regulation in at least at one time point, and 56 proteins were identified by MALDI-TOF/TOF-MS and database searching. Compared with control samples, 28 protein spots were up-regulated and 28 were down-regulated during at least one time point. The identified proteins, including chaperonine protein HSP60, caspase-8, calcium ion-binding protein, zinc ion-binding protein, actin-binding protein, proteolysis, fibrinolytic protease, glutamate dehydrogenase, gelsolin-like protein, lombricine kinase, coelomic cytolytic factor 1, manganous superoxide dismutase, extracellular globin-4, lysenin, intermediate filament protein, and tubulin, are involved in several processes, including transcription, translation, the tricarboxylic acid cycle, the cellular amino acid metabolic process, protein amino acid phosphorylation, glycolysis, and the glucose metabolic process. Thus, our study provides a functional profile of the Cd-responsive proteins in earthworms.

Creatine kinase and arginine kinase are the typical representatives of an eight-member phosphagen kinase family, which play important roles in the cellular energy metabolism of animals. The phylum Annelida underwent a series of evolutionary processes that resulted in rapid divergence and radiation of these enzymes, producing the greatest diversity of the phosphagen kinases within this phylum. Lombricine kinase (EC 2.7.3.5) is one of such enzymes and sequence information is rather limited compared to other phosphagen kinases. This study presents data on the cDNA sequences of lombricine kinase from two oligochaete species, the California blackworm (Lumbriculus variegatus) and the sludge worm (Tubifex tubifex). The deduced amino acid sequences are analyzed and compared with other selected phosphagen kinases, including two additional lombricine kinase sequences extracted from DNA databases and provide further insights in the evolution and position of these enzymes within the phosphagen kinase family. The data confirms the presence of a deleted region within the flexible loop (the GS region) of all six examined lombricine kinases. A phylogenetic analysis of these six lombricine kinases clearly positions the enzymes together in a small subcluster within the larger creatine kinase (EC 2.7.3.2) clade.

Annelids as a group express a variety of phosphagen kinases including creatine kinase (CK), glyocyamine kinase (GK), lombricine kinase (LK), taurocyamine kinase (TK) and a unique arginine kinase (AK) restricted to annelids. In prior work, we have determined and compared the intron/exon organization of the annelid genes for cytoplasmic GK, LK, AK, and mitochondrial TK and LK (MiTK and MiLK, respectively), and found that these annelid genes, irrespective of cytoplasmic or mitochondrial, have the same 8-intron/9-exon organization strikingly similar to mitochondrial CK (MiCK) genes. These results support the view that the MiCK gene is basal and ancestral to the phosphagen kinases unique to annelids. To gain a greater understanding of the evolutionary processes leading to the diversity of annelid phosphagen kinases, we determined for the first time the intron/exon organization of a cytoplasmic CK gene from a polychaete as well as that of another polychaete MiCK gene. These gene structures, coupled with a phylogenetic analyses of annelid enzymes and assessment of the fidelity of substrate specificity of some these phosphagen kinases, provide insight into the pattern of radiation of the annelid enzymes. Annelid phosphagen kinases appeared to have diverged in the following order (earliest first): (1) cytoplasmic AK, LK and TK, (2) GK, and (3) mitochondrial MiLK and MiTK. Interestingly, phylogenetic analyses showed that the above phosphagen kinases appear to be basal to all CK isoforms (mitochondrial, cytoplasmic and flagellar CKs). This somewhat paradoxical placement of CKs most likely reflects a higher rate of evolution and radiation of the annelid-specific LK, TK and GK genes than the CK isoform genes.

Creatine kinase (CK) is a member of a group of phosphoryl transfer enzymes called phosphagen kinases that play a key role in cellular energy transactions in animals. Three CK isoform gene families are known-cytoplasmic CK (CK), flagellar CK (fCK), and mitochondrial CK (MiCK). Each of the isoforms has a unique gene structure (intron/exon organization). A broad array of other phosphagen kinases is present in animals. Some of these enzymes are found only in annelids and closely related groups including glyocyamine kinase (GK), lombricine kinase (LK), taurocyamine kinase (TK), and a unique arginine kinase (AK) restricted to annelids. Phylogenetic analyses of these annelid phosphagen kinases indicate that they appear to have evolved from a CK-like ancestor. To gain a greater understanding of the relationship of the CK isoforms to the annelid enzymes, we have determined the intron/exon organization of the genes for the following phosphagen kinases: Eisenia LK, Sabellastarte AK, and Arenicola mitochondrial TK (MiTK). Analysis of genomic database for the polychaete Capitella sp. yielded two putative LK genes [cytoplasmic LK and mitochondrial LK (MiLK)]. The intron/exon organization of these genes was compared with available data for cytoplasmic and mitochondrial CKs, and an annelid GK. Surprisingly, these annelid genes, irrespective of whether they are cytoplasmic (LK, AK, and GK) or mitochondrial (MiTK and MiLK), had the same 8-intron/9-exon organization and were strikingly similar to MiCK genes sharing seven of eight splice junctions. These results support the view that the MiCK gene is basal and ancestral to the phosphagen kinases unique to annelids.

The giant tubeworm Riftia pachyptila lives at deep-sea hydrothermal vents along the East Pacific Rise and the Galapagos Rift. The large size and high growth rate of R. pachyptila is supported by an endosymbiotic relationship with a chemosynthetic bacterium. Elucidation of the regulation of energy metabolism of the giant tubeworm remains an interesting problem. The purpose of this study is to determine the cDNA sequence of phosphagen kinase, one of the most important enzymes in energy metabolism, and to characterize its function. Two phosphagen kinase cDNA sequences amplified from the cDNA library of R. pachyptila showed high derived amino acid sequence identity (74%) with those of cytoplasmic taurocyamine kinase (TK) and mitochondrial TK from an annelid Arenicola brasiliensis. The cytoplasmic form of the Riftia recombinant enzyme showed stronger activity for the substrates taurocyamine and also considerable activity for lombricine (21% that of taurocyamine). The mitochondrial form, which was structurally similar to mitochondrial creatine kinase, showed stronger activity for taurocyamine, and a broader activity for various guanidine compounds: glycocyamine (35% that of taurocyamine), lombricine (31%) and arginine (3%). Both forms showed no activity for creatine. The difference in substrate specificities between the cytoplasmic and mitochondrial forms might be attributable to the large difference in the amino acid sequence of the GS region and/or several key amino acid residues for establishing guanidine substrate specificity. Based on these results, we conclude that Riftia contains at least two forms of TK as phosphagen kinase. We also report the kinetic parameters, Km and kcat, of Arenicola and Riftia TKs for the first time. The Km values for taurocyamine of Arenicola and Riftia TKs ranged from 0.9 to 4.0 mM and appear to be comparable to those of other annelid-specific enzymes, lombricine kinase and glycocyamine kinase, but are significantly lower than those of Neanthes cytoplasmic and mitochondrial creatine kinases. Comparison of kcat/Km value in various annelid phosphagen kinases indicates that Arenicola mitochondrial TK has the highest catalytic efficiency (16.2 s−1 mM−1). In Arenicola TKs, the mitochondrial form has seven-fold higher efficiency than the cytoplasmic form.

Taurocyamine kinase (TK) is a member of the highly conserved family of phosphagen kinases that includes creatine kinase (CK) and arginine kinase. TK is found only in certain marine annelids. In this study we used PCR to amplify two cDNAs coding for TKs from the polychaete Arenicola brasiliensis, cloned these cDNAs into the pMAL plasmid and expressed the TKs as fusion proteins with the maltose-binding protein. These are the first TK cDNA and deduced amino acid sequences to be reported. One of the two cDNA-derived amino acid sequences of TKs shows a high amino acid identity to lombricine kinase, another phosphagen kinase unique to annelids, and appears to be a cytoplasmic isoform. The other sequence appears to be a mitochondrial isoform; it has a long N-terminal extension that was judged to be a mitochondrial targeting peptide by several on-line programs and shows a higher similarity in amino acid sequence to mitochondrial creatine kinases from both vertebrates and invertebrates. The recombinant cytoplasmic TK showed activity for the substrates taurocyamine and lombricine (9% of that of taurocyamine). However, the mitochondrial TK showed activity for taurocyamine, lombricine (30% of that of taurocyamine) and glycocyamine (7% of that of taurocyamine). Neither TK catalyzed the phosphorylation of creatine. Comparison of the deduced amino acid sequences of mitochondrial CK and TK indicated that several key residues required for CK activity are lacking in the mitochondrial TK sequence. Homology models for both cytoplasmic and mitochondrial TK, constructed using CK templates, provided some insight into the structural correlation of differences in substrate specificity between the two TKs. A phylogenetic analysis using amino acid sequences from a broad spectrum of phosphagen kinases showed that annelid-specific phosphagen kinases (lombricine kinase, glycocyamine kinase and cytoplasmic and mitochondrial TKs) are grouped in one cluster, and form a sister-group with CK sequences from vertebrate and invertebrate groups. It appears that the annelid-specific phosphagen kinases, including cytoplasmic and mitochondrial TKs, evolved from a CK-like ancestor(s) early in the divergence of the protostome metazoans. Furthermore, our results suggest that the cytoplasmic and mitochondrial isoforms of TK evolved independently.

Creatine kinase (CK) catalyzes the reversible conversion of creatine and ATP to phosphocreatine and ADP, thereby helping maintain energy homeostasis in the cell. Here we report the first X-ray structure of CK bound to a transition-state analogue complex (CK-TSAC). Cocrystallization of the enzyme from Torpedo californica (TcCK) with ADP-Mg(2+), nitrate, and creatine yielded a homodimer, one monomer of which was liganded to a TSAC complex while the second monomer was bound to ADP-Mg(2+) alone. The structures of both monomers were determined to 2.1 A resolution. The creatine is located with the guanidino nitrogen cis to the methyl group positioned to perform in-line attack at the gamma-phosphate of ATP-Mg(2+), while the ADP-Mg(2+) is in a conformation similar to that found in the TSAC-bound structure of the homologue arginine kinase (AK). Three ligands to Mg(2+) are contributed by ADP and nitrate and three by ordered water molecules. The most striking difference between the substrate-bound and TSAC-bound structures is the movement of two loops, comprising residues 60-70 and residues 323-332. In the TSAC-bound structure, both loops move into the active site, resulting in the positioning of two hydrophobic residues (one from each loop), Ile69 and Val325, near the methyl group of creatine. This apparently provides a specificity pocket for optimal creatine binding as this interaction is missing in the AK structure. In addition, the active site of the transition-state analogue complex is completely occluded from solvent, unlike the ADP-Mg(2+)-bound monomer and the unliganded structures reported previously.

Phosphagen kinases constitute a large family of enzymes catalyzing the reversible phosphorylation of guanidino acceptor compounds. These guanidino substrates differ substantially in size and chemical properties. In spite of the appearance of X-ray crystal structures for two members of this family, creatine kinase (CK) and arginine kinase (AK), the structural correlates of substrate specificity remain to be fully elucidated. We have determined the cDNA and deduced amino acid sequences for lombricine (guanidinethylphosphoserine) kinase (LK) from the echiuroid worm Urechis caupo and expressed the cDNA in Escherichia coli. The recombinant protein was purified by affinity chromatography and showed high capacity for phosphorylation of lombricine. Phosphagen kinases consist of a small, N-terminal domain and a much larger domain connected by a linker sequence. A key event in catalysis in CK and AK, and certainly all other phosphagen kinases, is a large conformational change involving involving a rotation of the two domains and the movement of two highly conserved flexible loops (one located in the small domain; the other located in the large domain of these enzymes) which clamp down on the substrates. Multiple sequence alignments of Urechis LK with the only other LK sequence available and CK, AK and glycocyamine kinase sequences, confirm the importance of the small flexible loop located in the N-terminal domain of phosphagen kinases as one component of the structural determinants of guanidine specificity. The role of the other flexible loop in the large domain in terms of substrate specificity remains questionable.

Arginine kinases were isolated from the cephalopods Nautilus pompilius, Octopus vulgaris, and Sepioteuthis lessoniana, and the cDNA-derived amino acid sequences have been determined. Although the origin and evolution of cephalopods have long been obscure, this work provides the first molecular evidence for the phylogenetic position of Cephalopoda in molluscan evolution. A crystal structure for Limulus arginine kinase showed that four amino acid residues (Ser63, Gly64, Val65, and Tyr68) are hydrogen-bonded with the substrate arginine. We introduced three independent mutations, Ser63→ Gly, Ser63 → Thr, and Tyr68 → Ser, in Nautilus arginine kinase. One of the mutants had a considerably reduced substrate affinity, accompanied by a decreasedV max. In other mutants, the activity was lost almost completely. It is known that substantial conformational changes take place upon substrate binding in arginine kinase. We hypothesize that the hydrogen bond between Asp62 and Arg193stabilizes the closed, substrate-bound state. Site-directed mutagenesis studies strongly support this hypothesis. The mutant (Asp62→ Gly or Arg193 → Gly), which destabilizes the maintenance of the closed state and/or perhaps disrupts the unique topology of the catalytic pocket, showed only a very weak activity (0.6–1.5% to the wild-type).

Lombricine kinase (LK) from the body wall muscle of the earthworm Eisenia foetida was purified to homogeneity. The enzyme was shown to be a dimer consisting of 40 kDa subunits. The cDNA-derived amino acid sequence of 370 residues of Eisenia LK was determined. The validity of the sequence was supported by chemical sequencing of internal tryptic peptides. This is the first reported lombricine kinase amino acid sequence. Alignment of Eisenia LK with those of creatine kinases (CKs), arginine kinases (AKs) and glycocyamine kinase (GK) suggested a region displaying remarkable amino acid deletions (referred to GS region), as a possible candidate for guanidine substrate recognition site. A phylogenetic analysis using amino acid sequences of all four phosphagen kinases indicates that CK, GK and LK probably evolved from a common immediate ancestor protein.

The two-domain taurocyamine kinase (TK) from Paragonimus westermani was suggested to have a unique substrate binding mechanism. We performed site-directed mutagenesis on each domain of this TK and compared the kinetic parameters Km(Tc) and Vmax with that of the wild-type to determine putative amino acids involved in substrate recognition and binding. Replacement of Y84 on domain 1 and Y87 on domain 2 with R resulted in the loss of activity for the substrate taurocyamine. Y84E mutant has a dramatic decrease in affinity and activity for taurocyamine while Y87E has completely lost catalytic activity. Substituting H and I on the said positions also resulted in significant changes in activity. Mutation of the residues A59 on the GS region of domain 1 also caused significant decrease in affinity and activity while mutation on the equivalent position on domain 2 resulted in complete loss of activity.

Taurocyamine kinase (TK) is an enzyme that catalyzes the reversible transfer of a phosphate between ATP and taurocyamine. Annelid TKs were suggested to have evolved from a CK ancestor. However, TKs from the lung fluke Paragonimus westermani comprised another lineage. Construction of phylogenetic tree and comparison of exon/intron organization showed that P. westermani TK and other trematode TKs evolved from a molluscan arginine kinase (AK) gene. Exon shuffling probably caused the changes in amino acid sequence thereby changing the affinity from AK to TK. The present study provides new insights on the evolution of phosphagen kinases found in trematodes.

The goal of this study was to identify promising new biomarkers of phenanthrene by identifying differentially expressed proteins in Eisenia fetida after exposure to phenanthrene. Extracts of earthworm epithelium collected at days 2, 7, 14, and 28 after phenanthrene exposure were analyzed by two dimensional electrophoresis (2-DE) and quantitative image analysis. Comparing the intensity of protein spots, 36 upregulated proteins and 45 downregulated proteins were found. Some of the downregulated and upregulated proteins were verified by MALDI-TOF/TOF-MS and database searching. Downregulated proteins in response to phenanthrene exposure were involved in glycolysis, energy metabolism, chaperones, proteolysis, protein folding and electron transport. In contrast, oxidation reduction, oxygen transport, defense systems response to pollutant, protein biosynthesis and fatty acid biosynthesis were upregulated in phenanthrene-treated E. fetida. In addition, ATP synthase b subunit, lysenin-related protein 2, lombricine kinase, glyceraldehyde 3-phosphate dehydrogenase, actinbinding protein, and extracellular globin-4 seem to be potential biomarkers since these biomarker were able to low levels (2.5 mg kg(-1)) of phenanthrene. Our study provides a functional profile of the phenanthrene-responsive proteins in earthworms. The variable levels and trends in these spots could play a potential role as novel biomarkers for monitoring the levels of phenanthrene contamination in soil ecosystems.

Of the six phosphagen kinases found in animals, the primary structure is known only for creatine kinase. Here we report three cDNA-derived or chemically determined amino acid sequences of two kinds of phosphagen kinases: a glycocyamine kinase from the polychaete Neanthes diversicolor (Annelida) and arginine kinase from the abalone Nordotis madaka (Mollusca) and the shrimp Penaeus japonicus (Arthropoda). Like vertebrate creatine kinases are monomers. These enzymes consist of 350 to 390 amino acid residues, and have a calculated molecular mass of 39,900 to 44,500 Da. Neanthes glycocyamine kinase shows 50 to 58% sequence similarity with vertebrate and invertebrate creatine kinases, having the greatest similarity (57 to 58%) with vertebrate mitochondrial creatine kinase isoform. It shows lower, but significant similarity (37 to 39%) with invertebrate arginine kinases. The sequence similarity between Nordotis and Penaeus arginine kinases is 51%. A phylogenetic tree constructed from 14 amino acid sequences of phosphagen kinases showed that they can be separated into three major clusters corresponding to creatine kinase, glycocyamine kinase and arginine kinase. The cluster of glycocyamine kinase is apparently closer to that of creatine kinase than arginine kinase. The cluster of creatine kinase is composed of several subclusters, each corresponding to three vertebrate isoforms and the invertebrate enzyme.

Escherichia coli O157:H7 is an intestine-inhabiting bacterium associated with many severe disease outbreaks worldwide. It may enter the soil environment with the excreta of infected animals (e.g., horses, cattle, chickens) and humans. Earthworms can protect themselves against invading pathogens because of their efficient innate defense system. Identification of differential proteomic responses to E. coli O157:H7 may provide a better understanding of the survival mechanisms of the earthworm Eisenia fetida that lives in E. coli O157:H7-polluted environments. Whole earthworm extracts, collected at days 7, 14, 21, and 28 after E. coli O157:H7 stress, were analyzed by two-dimensional gel electrophoresis and quantitative image analysis. In total, 124 proteins demonstrated significant regulation at least at one time point, and 52 proteins were identified by matrix-assisted laser desorption/ionization-tandem time-of-flight mass spectrometry and database searching. Compared with control samples, 11 protein spots were up-regulated and 41 were down-regulated for at least one time point. The identified proteins, including heat shock protein 90, fibrinolytic protease 0, gelsolin-like protein, lombricine kinase, coelomic cytolytic factor-1, manganous superoxide dismutase, catalase, triosephosphate isomerase, extracellular globin-4, lysenin, intermediate filament protein, and glyceraldehyde-3-phosphate dehydrogenase, are involved in several processes, including transcription, translation, the tricarboxylic acid cycle, and the glucose metabolic process. Thus, our study provides a functional profile of the E. coli O157:H7-responsive proteins in earthworms. We suggest that the variable levels and trends in these spots on the gel may be useful as biomarker profiles to investigate E. coli O157:H7 contamination levels in soils.

In creatine kinases (CKs), the amino acid residue-96 is a strictly conserved arginine. This residue is not directly associated with substrate binding, but it is located close to the binding site of the substrate creatine. On the other hand, the residue-96 is known to be involved in expression in the substrate specificity of various other phosphagen (guanidino) kinases, since each enzyme has a specific residue at this position: arginine kinase (Tyr), glycocyamine kinase (Ile), taurocyamine kinase (His) and lombricine kinase (Lys). To gain a greater understanding of the role of residue-96 in CKs, we replaced this residue in zebra fish Danio rerio cytoplasmic CK with other 19 amino acids, and expressed these constructs in Escherichia coli. All the twenty recombinant enzymes, including the wild-type, were obtained as soluble form, and their activities were determined in the forward direction. Compared with the activity of wild-type, the R96K mutant showed significant activity (8.3% to the wild-type), but 10 mutants (R96Y, A, S, E, H, T, F, C, V and N) showed a weak activity (0.056-1.0%). In the remaining mutants (R96Q, G, M, P, L, W, D and I), the activity was less than 0.05%. Our mutagenesis studies indicated that Arg-96 in Danio CK can be substituted for partially by Lys, but other replacements caused remarkable loss of activity. From careful inspection of the crystal structures (transition state analog complex (TSAC) and open state) of Torpedo cytoplasmic CK, we found that the side chain of R96 forms hydrogen bonds with A339 and D340 only in the TSAC structure. Based on the assumption that CKs consist of four dynamic domains (domains 1-3, and fixed domain), the above hydrogen bonds act to link putative domains 1 and 3 in TSAC structure. We suggest that residue-96 in CK and equivalent residues in other phosphagen kinases, which are structurally similar, have dual roles: (1) one involves in distinguishing guanidino substrates, and (2) the other plays a key role in organizing the hydrogen-bond network around residue-96 which offers an appropriate active center for the high catalytic turnover. The mode of development of the network appears to be unique each phosphagen kinase, reflecting evolution of each enzyme.

Hypotaurocyamine kinase (HTK) is a member of the highly conserved family of phosphagen kinases that includes creatine kinase (CK) and arginine kinase (AK). HTK is found only in sipunculid worms, and it shows activities for both the substrates hypotaurocyamine and taurocyamine. Determining how HTK evolved in sipunculids is particularly insightful because all sipunculid-allied animals have AK and only some sipunculids have HTK. We determined the cDNA sequence of HTK from the sipunculid worm Siphonosoma cumanense for the first time, cloned it in pMAL plasmid and expressed it in E. coli as a fusion protein with maltose-binding protein. The cDNAderived amino acid sequence of Siphonosoma HTK showed high amino acid identity with molluscan AKs. Nevertheless, the recombinant enzyme of Siphonosoma HTK showed no activity for the substrate arginine, but showed activity for taurocyamine. Comparison of the amino acid sequences of HTK and AK indicated that the amino acid residues necessary for the binding of the substrate arginine in AK have been completely lost in Siphonosoma HTK sequence. The phylogenetic analysis indicated that the HTK amino acid sequence was placed just outside the molluscan AK cluster, which formed a sister group with the arthropod and nematode AKs. These results suggest that Siphonosoma HTK evolved from a gene for molluscan AK. Moreover, to confirm this assertion, we determined by PCR that the gene for Siphonosoma HTK has a 5-exon/4-intron structure, which is homologous with that of the molluscan AK genes. Further, the positions of splice junctions were conserved exactly between the two genes. Thus, we conclude that Siphonosoma HTK has evolved from a primordial gene for molluscan AK.

The purpose of this study is to elucidate the mechanisms of guanidine substrate specificity in phosphagen kinases, including creatine kinase (CK), glycocyamine kinase (GK), lombricine kinase (LK), taurocyamine kinase (TK) and arginine kinase (AK). Among these enzymes, LK is unique in that it shows considerable enzyme activity for taurocyamine in addition to its original target substrate, lombricine. We earlier proposed several candidate amino acids associated with guanidine substrate recognition. Here, we focus on amino-acid residue 95, which is strictly conserved in phosphagen kinases: Arg in CK, Ile in GK, Lys in LK and Tyr in AK. This residue is not directly associated with substrate binding in CK and AK crystal structures, but it is located close to the binding site of the guanidine substrate. We replaced amino acid 95 Lys in LK isolated from earthworm Eisenia foetida with two amino acids, Arg or Tyr, expressed the modified enzymes in Escherichia coli as a fusion protein with maltose-binding protein, and determined the kinetic parameters. The K95R mutant enzyme showed a stronger affinity for both lombricine (Km=0.74 mM and kcat/Km=19.34 s−1 mM−1) and taurocyamine (Km=2.67 and kcat/Km=2.81), compared with those of the wild-type enzyme (Km=5.33 and kcat/Km=3.37 for lombricine, and Km=15.31 and kcat/Km=0.48 for taurocyamine). Enzyme activity of the other mutant, K95Y, was dramatically altered. The affinity for taurocyamine (Km=1.93 and kcat/Km=6.41) was enhanced remarkably and that for lombricine (Km=14.2 and kcat/Km=0.72) was largely decreased, indicating that this mutant functions as a taurocyamine kinase. This mutant also had a lower but significant enzyme activity for the substrate arginine (Km=33.28 and kcat/Km=0.01). These results suggest that Eisenia LK is an inherently flexible enzyme and that substrate specificity is strongly controlled by the amino-acid residue at position 95.

▪ Abstract Phosphagens are phosphorylated guanidino compounds that are linked to energy state and ATP hydrolysis by corresponding phosphagen kinase reactions: phosphagen + MgADP + H+↔ guanidine acceptor + MgATP. Eight different phosphagens (and corresponding phosphagen kinases) are found in the animal kingdom distributed along distinct phylogenetic lines. By far, the creatine phosphate/creatine kinase (CP/CK) system, which is found in the vertebrates and is widely distributed throughout the lower chordates and invertebrates, is the most extensively studied phosphagen system. Phosphagen kinase reactions function in temporal ATP buffering, in regulating inorganic phosphate (Pi) levels, which impacts glycogenolysis and proton buffering, and in intracellular energy transport. Phosphagen kinase reactions show differences in thermodynamic poise, and the phosphagens themselves differ in terms of certain physical properties including intrinsic diffusivity. This review evaluates the distribution of phosphagen systems and tissue-specific expression of certain phosphagens in an evolutionary and functional context. The role of phosphagens in regulation of intracellular Pi levels likely evolved early. Thermodynamic poise of the phosphagen kinase reaction profoundly impacts this capacity. Furthermore, it is hypothesized that the capacity for intracellular targeting of CK evolved early as a means of facilitating energy transport in highly polarized cells and was subsequently exploited for temporal ATP buffering and dynamic roles in metabolic regulation in cells displaying high and variable rates of aerobic energy production.

A diverse array ofphosphagen kinases [arginine kinase (AK), lombricine kinase (LK)], glycocyamine kinase (GK), taurocyamine kinase (TK), and creatine kinase (CK) is ,found in the animal kingdom (see reJ: 1 for a review). These reactions appear to junction in the temporal bu#ering of ATP in muscles during energy de&its such as might occur during burst contraction or anoxia (2, 3). In many vertebrate tissues, a distinct mitochondrial isoenzyme of CK is present, and it may play a special role in the intracellular transport of high energy phosphate (4). In this study, we investigated whether mitochondrial activities ofphosphagen kinases are present in invertebrate muscles. Our results show that AK is present in mitochondria from a crustacean. However, phosphagen kinases are lacking in mitochondria from insect fright muscles, molluscan cardiac and smooth muscle, andpolychaete and oligochaete body wall musculature. It appears that mitochondrial activities of phosphagen kinases are not widely distributed in the invertebrates. These data, in conjunction with previous studies on the physico-chemical nature of the interaction of phosphagen kinases with mitochondria (5, 6), suggest that mitochondrial compartmentation of phosphagen kinases may have evolved independently in two major animal groups. Mitochondrial CK in vertebrate muscle constitutes the proximal end of the so-called phosphocreatine shuttle (4). According to the shuttle model, CK catalyzes the phosphorylation of creatine to phosphocreatine using newly synthesized ATP. The resulting phosphocreatine is then thought to diffuse from the mitochondrion to sites of ATP use (myofibrils, ion transport ATPases), where it is used

Arginine kinase belongs to the family of enzymes, including creatine kinase, that catalyze the buffering of ATP in cells with fluctuating energy requirements and that has been a paradigm for classical enzymological studies. The 1.86-Å resolution structure of its transition-state analog complex, reported here, reveals its active site and offers direct evidence for the importance of precise substrate alignment in the catalysis of bimolecular reactions, in contrast to the unimolecular reactions studied previously. In the transition-state analog complex studied here, a nitrate mimics the planar γ-phosphoryl during associative in-line transfer between ATP and arginine. The active site is unperturbed, and the reactants are not constrained covalently as in a bisubstrate complex, so it is possible to measure how precisely they are pre-aligned by the enzyme. Alignment is exquisite. Entropic effects may contribute to catalysis, but the lone-pair orbitals are also aligned close enough to their optimal trajectories for orbital steering to be a factor during nucleophilic attack. The structure suggests that polarization, strain toward the transition state, and acid-base catalysis also contribute, but, in contrast to unimolecular enzyme reactions, their role appears to be secondary to substrate alignment in this bimolecular reaction.

Earthworms were subjected to environmental anoxia (200 min) and electrical stimulation (5 min, 6 V, 50 Hz). The levels of high-energy phosphate compounds and the intracellular pH were monitored during anoxia, muscular contraction, and recovery by in vivo phosphorus-31 nuclear magnetic resonance (31P-NMR). Several key metabolites were determined by enzymatic analysis and reversed-phase high-performance liquid chromatography of perchlorate extracts. Because lombricine, the phosphagen phosphate acceptor of earthworms, is a phosphodiester, 31P-NMR permitted direct analysis of the extent of phosphorylation of the lombricine pool in vivo. Total lombricine, lombricine phosphate, ATP, and H+ were measured by NMR, and free ADP was calculated from the lombricine kinase equilibrium constant. The ADP concentration was not significantly changed by anoxia, but it rose threefold after stimulation. L-Lactate accumulated on stimulation, whereas multiple end products (L-lactate, alanine, succinate, and glutamine) were formed during environmental anaerobiosis.

1. Phospholombricine and phosphoarginine are the two naturally occurring phosphagens in the facultative anaerobeTubifex (Table 1). During experimental anaerobiosis concentrations of both phosphagens decreased within the initial 6–12 h (Fig. 1). 2. Lombricine has been isolated from the worms with a yield of 7.2 μmoles per g d.wt. and purified to homogeneity. Phospholombricine was obtained by enzymatic transphosphorylation ofd-lombricine. The compound was also isolated from the worms by a specific procedure. 3. The 1,473-fold purified enzyme lombricine kinase has a specific activity of 30 U/mg of protein at 25°C (Table 3) and a turnover number of 2,100 min−1. The molecular weight was estimated to be 69,000. 4. Kinetic and regulatory properties of both phosphagen kinases and of adenylate kinase (myokinase) are reported (Fig. 2, Table 4). 5. In living worms the ATP/ADP ratio, or the energy charge value, probably determines whether the phosphagens are synthesized or utilized.

The active cysteinyl residues of dimeric taurocyamine kinase from Arenicola marina were labelled with N -ethyl-[1- 14 C]maleimide. The resulting inactivated N -ethyl-[1- 14 C]succinimido enzyme was then subjected to tryptic hydrolysis. The peptide containing the labelled essential cysteinyl residue was isolated. The amino acid sequence of this peptide is Leu-Gly-Tyr-Leu-Gly-Thr-[ 14 C]Cys-Pro-Thr-Asn-Ile-Gly-Thr-Gly-Leu-Arg. This sequence is very similar to that of homologous ATP:guanidine phosphotransferases previously studied, arginine kinase from Homarus vulgaris muscle, creatine kinase from ox brain and ox muscle, and from rabbit muscle, and lombricine kinase from Lubricus terrestris .

Interaction of N-ethylmaleimide with the essential cysteinyl residue of ATP:l-arginine phosphotransferase from Homarus vulgaris muscle has been studied by means of difference spectrophotometry and labelling with radioactive N-ethyl-[1-14C]maleimide. Cysteine and glutathione were used as model compounds reacting with the inhibitor. The difference spectrum at 238 nm observed with the l-arginine-arginine kinase complex might be ascribed to the modification of ionized – SH groups. The absorption change observed near 287 nm. produced by tyrosyl perturbation, is the same when the enzyme reacts with the inhibitor or with l-arginine. Labelling data give evidence of a significant protection of the essential thiol group by l-arginine against N-ethyl-[1-14C]maleimide. This cysteinyl residue is included in the tryptic peptide T1A the amino acid sequence of which, recently determined, is very similar to that to the homologous peptides of muscle and brain rabbit creatine kinases and of earth-worm muscle lombricine kinase.

1. 1. The immunochemocal properties of a number of phosphagen kinases from vertebrate and invertebrate muscle have been studied. 2. 2. By gel diffusion methods, cross-reactions were occasionally noticed between similar enzymes of different species, demonstrating immunological analogies within some zoological groups. 3. 3. For creatine kinase, these results contrast with the absence of cross-reactions reported between the two pure isozymic forms (muscle and brain type) of one species. 4. 4. No cross-reactions occur between arginine kinase and creatine kinase, nor between these enzymes and the other phosphagen kinases. 5. 5. On the other hand, cross-reactions were detected between lombricine, opheline and taurocyamine kinases, the three enzymes specific for oligochaetous and polychaetous annelids. 6. 6. All phosphagen kinases studied were inhibited by their specific antiserum, but no cross-inhibition occurred between heterologous antigens. 7. 7. The results suggest that the inhibition involves steric hindrance and that the antibodies are formed against other sites than the active sites. 8. 8. It is suggested that mild denaturation of the phosphagen kinases could create similar antigenic determinants on their molecules, as has been found for lactic dehydrogenases. 9. 9. From a phylogenetic point of view, the immunochemical study of native phosphagen kinases show the partial conservation of the protein structure through evolution. 10. 10. The analogies so noticed seem to depend on the animal origin of the protein rather than on its specificity toward the natural guanidine substrate.

Summary The molecular weights of four new ATP : guanidino phosphotransferases (EC Class 2.7.3) (taurocyamine kinase (EC 2.7.3.4), glycocyamine kinase, hypotauro-cyamine kinase (EC 2.7.3,6) and lombricine kinase (EC 2.7.3.5)) have been determined by gel filtration on Sephadex G-100 and density-gradient ultracentrifugation, using pure creatine- and pure arginine-kinases as standard proteins (respective molecular weights 81 000 and 43 000). The molecular weights of homogenous preparations of taurocyamine- and lombricine-kinases determined by analytical ultracentrifugation are the same as those of the partially purified preparations of the same enzymes determined by other techniques. The molecular weights of these proteins lie in the range of 80 000–87 000 (taurocyamine kinase), 83 000 (hypotaurocyamine kinase), 79 000–82 000 (glycocyamine kinase) to 74 000–77 000 (lombricine kinase).

The active thiol group of lombricine kinase from Lumbricus terrestris muscle was labelled with N-ethyl-[1-14C]maleimide. The resulting inactivated N-ethyl-[1-14C]succinimido enzyme was then subjected to tryptic hydrolysis. The peptide containing the labelled essential thiol group was isolated and found to contain: Leu-Gly-Tyr-Ile-Thr-[14C]Cys-Pro-Gly-Ser-Asn-Leu-Gly-Thr-Leu-Arg. The amino acid sequence around this thiol group was very similar with that of homologous ATP: guanidine phosphotransferases previously studied, arginine kinase from Homarus vulgaris muscle, creatine kinases from ox brain and ox muscle and from rabbit muscle. In addition among the other enzymes of this group, lombricine kinase is of special interest since it is the only dimeric enzyme of molecular weight ≃ 80000 which possesses only one essential thiol group and one nucleotide binding site per two subunits.

Summary Determination of molecular weights and number of subunits of various Phosphagen kinases 1. The sedimentation constants of lobster (Homarus vulgaris) and crab (Cancer pagurus) arginine kinases (ATP:arginine phosphotransferases, EC 2.7.3.3) and of lombricine kinase (ATP:lombricine phosphotransferase, EC 2.7.3.5) and taurocyamine kinase (ATP:taurocyamine phosphotransferase, EC 2.7.3.4) from earthworm (Lumbricus terrestris) and arenicola (Arenicola marina), respectively, were determined. 2. Their molecular weights have been measured in their native and dissociated state by the methods of Archibald and Y phantis 9. Dissociation was carried out in 6 M guanidine hydrochloride, containing β-mercaptoethanol. 3. Both arginine kinases were monomers with a molecular weight of about 40 000. Alternatively, lombricine and taurocyamine kinases were shown to be dimers with two subunits of about 40 000 each.

Comparative study of the reactive SH groups of ATP:guanidine phosphotransferases 1. 1. With 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) in the presence of urea, 6 SH groups are titrated in ATP:creatine phosphotransferase (EC 2.7.3.2), ATP:arginine phosphotransferase (EC 2.7.3.3) and ATP:lombricine phosphotransferase (EC 2.7.3.5); 14 SH groups are found in ATP:taurocyamine phosphotransferase (EC 2.7.3.4) and 16 in ATP:guanidinoacetate phosphotransferase (EC 2.7.3.1). In the absence of urea, only 1 SH group is titrated in lombricine kinase, 2 in creatine and taurocyamine kinases, and 6 in arginine and glycocyamine kinases. 2. 2. At pH 8.5, 3 of the SH groups of arginine kinase react at once with DTNB; at pH 7, only one SH is immediately titratable. The blocking of this SH group results in the complete inhibition of the enzyme. l-Arginine efficiently antagonizes the inhibitor; Mg-ATP and Mg-ADP decrease the rate of alkylation but do not restore the inactivation of arginine kinase. 3. 3. Stoichiometric inhibition by DTNB reveals the presence of one reactive SH group in arginine and lombricine kinases and of 2 essential SH groups in glycocyamine, creatine and taurocyamine kinases. Guanidine substrates, arginine and lombricine, efficiently protect their respective enzymes against inactivation by DTNB; in contrast glycocyamine and creatine do not protect their corresponding enzymes. Moreover, Mg-ATP protects glycocyamine and creatine kinases but not the arginine and lombricine kinases. Taurocyamine kinase is intermediate between these 2 groups of enzymes: it is protected from DTNB by both guanidine and nucleotide substrates. 4. 4. Fingerprints of N-[I-14C]ethylmaleimide-labelled creatine, taurocyamine and lombricine kinases show the presence of approximately the same number of peptides, 46, which are mainly neutral or basic. Arginine kinase, the molecular weight of which is half that of the other 3 enzymes, produces nearly the same number of peptides, 45–48. On autoradiograms of the fingerprints of the 4 enzymes, the main radioactivity seems to be situated in the same peptide.

Summary 1. ATP:taurocyamine phosphotransferase (EC 2.7.3.4) anci ATP:lombricine phosphotransferase (EC 2.7.3.5), prepared according to the methods described, are homogeneous on ultra-centrifugation. S 20, w values and molecular weights are determined. 2. Determination with p -chloromercuribenzoate or N -ethylmaleimide at pH 7 in the presence of urea, or with 5,5′-dithiobis (2-nitrobenzoic acid) at pH 6.8, revealed 6 SH groups in lombricine kinase and 8–9 in taurocyamine kinase. The latter enzyme exhibits 12 SH groups when titration with p -chloromercuribenzoate is carried out at pH 4.6. 3. The decrease of both enzymic activities is proportional to the amount of N -ethylmaleimide or p -chloromercuribenzoate bound to the enzymes. The stoichiometric titration of SH groups compared with the parallel loss of transferase activity shows that taurocyamine kinase possesses 4 reactive SH groups and lombricine kinase only one. It is concluded that the active site of ATP :guanidino phosphotransferases seems to involve only one SH group.

Taurocyamine kinase (TK) was previously reported to be restricted to certain marine annelids; however, the present study has proven otherwise. The lung fluke Paragonimus westermani has a contiguous two-domain TK with a mass of 80216Da consisting of 713 amino acid residues sharing higher sequence identity with molluscan arginine kinase (AK). Both domains of P. westermani TK have significant activity for the substrate taurocyamine and exhibited synergism during substrate binding. Since TK plays a key role in energy metabolism and is not present in mammals, inhibitors against P. westermani TK could be effective novel chemotherapeutic agents and could be utilized for the development of specific diagnostic tools for the detection of paragonimiasis.

Of the dimeric phosphagen kinases (Mr= 80000) studied, lombricine kinase is the only one which contains only one essential thiol group and one binding site for ADP-Mg. These facts suggest a non-identity between the two subunits of this enzyme. The reversible labeling of the essential thiol group of this protein with 2,4-dinitrofluorobenzene, followed by alkylation of the remaining thiol groups, allowed the separation of the two subunits by means of a Sepharose-mercurial column. The Sepharose-mercurial was prepared by treatment of Sepharose 4B with p-aminophenyl mercuric acetate. Amino-acid analyses, N- and C-terminal determinations and fingerprintings were performed to detect the differences in the primary structure between the two subunits. Furthermore, the Sepharose-mercurial column was used to purify the tryptic peptide containing the essential thiol group of lombricine kinase. By this process, it was possible to obtain, in one step, the peptide in a pure state. It is interesting to point out the applicability of this method for the purification of peptides or proteins containing essential thiol groups which can be specifically labelled by reversible inhibitors.