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Background The CDA 79A > C (K27Q, rs2072671) functional SNP has recently shown a crucial role in the pharmacogenetics of cytidine-based anticancer drugs widely administered to different subsets of patients. Current gold standard in screening for the CDA rs2072671 is the sequence-based genotyping method. Here we developed a novel, rapid Allele-Specific PCR method for CDA rs2072671 genotyping. Methods DNA was extracted from 324 healthy individuals from two different populations (Italian and Han Chinese). CDA rs2072671 genotyping was performed by Allele-Specific PCR. Sequencing was performed to validate the test results. Results obtained from population screening were compared to that already available in HapMap and in the literature. Results Samples analyzed were successfully genotyped and the results were confirmed by sequencing. Genotype distribution does not differ significantly from that previously reported for each relative ethnic group. Also, the world-wide distribution of the CDA rs2072671 SNP is reported. A striking difference is present among the main ethnicities (p = 1.715 × 10−77), with CDA*27Q allele showing the lowest frequency in African group (9.7%) and the highest in Caucasians (35.9%). Conclusion This Allele-Specific PCR method is a useful tool in pharmacogenetics research and a valid and reliable alternative for CDA rs2072671 screening where sequencing or Real-Time PCR is not available.

Cytidine deaminase (CDA) is a pyrimidine salvage pathway enzyme that catalyzes the hydrolytic deamination of cytidine and deoxycytidine to their corresponding uracil nucleosides. CDA also catalyzes the inactivation of some chemotherapeutic nucleoside analogues such as cytosine arabinoside and gemcitabine. CDA 79A > C (K27Q, rs2072671) and 208G > A (A70T, rs60369023) were found to be associated either with clinical outcomes as well as with pharmacokinetics and toxicity of drugs administered to different subsets of patients. In this paper we reported two PCR-based methods for CDA 79A > C (K27Q) and 208G > A (A70T) genotyping and tested their feasibility using DNA extracted from whole blood as well as from buccal swabs. The aim of this study was also to assess the distribution of genotypic variants in a central Italy population. The allele frequencies were 56.3% (K*) and 43.7% (Q*) for K27Q and 100% (A*) and 0% (T*) for A70T. The genotype frequencies were 32.8% (K*/K*), 46.9% (K*/Q*) and 20.3% (Q*/Q*) for K27Q. The genotype frequencies did not deviate from Hardy-Weinberg equilibrium. The results were compared with those of other reported populations. They showed marked ethnic group differences.

Donkey’s milk may be considered a valid alternative, for infant nutrition, to powdered milks, soybean milk or other formulas, since its composition in lipids and proteins is very close to human milk. The aim of the present study is to characterize “donkey’s milk” product, especially with regard to the protein fractions. Three different chromatographic approaches for donkey’s milk proteins separation are described, based on their different isoelectric points, hydrophobicity and molecular mass. The proteins obtained were further separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis and identified by N-terminal sequencing. α S1 - and β-caseins, lysozyme, α-lactalbumin, β-lactoglobulin were identified. Furthermore, the content of α-lactalbumin, β-lactoglobulin, and lysozyme in donkey’s milk was determined by a reversed-phase HPLC method. The β-lactoglobulin and α-lactalbumin content was 3.75 and 1.8 mg/ml, respectively (mean values). The present study showed the nutritional properties of donkey’s milk characterized by low casein and high lysozyme content (1.0 mg/ml) compared with other kinds of milks.

An investigation was made of the role exerted by some residues supposed to be involved in the intersubunit interaction and also in the catalytic site of homotetrameric human cytidine deaminase (T-CDA). Attention was focused on Y33, Y60, R68, and F137 residues that are a part of a conserved region in most T-CDAs. Hence, a series of site-directed mutagenesis experiments was set up obtaining seven mutants: Y60G, Y33G, Y33F Y33S, F137A, R68G, and R68Q. Each active purified mutant protein was characterized kinetically, with a series of substrates and inhibitors, and the effect of temperature on enzyme activity and stability was also investigated. Circular dichroism (CD) experiments at different temperatures and in presence of small amounts of sodium dodecyl sulphate (SDS) were performed in all the soluble mutant CDAs. The results obtained by site-directed mutagenesis studies were compared to the crystallographic data of B. subtilis CDA and E. coli CDA and to molecular modeling studies previously performed on human CDA. The mutation of Y60 to glycine produced an enzyme with a more compact quaternary structure with respect to the wild-type; this mutation did not have a dramatic effect on cytidine deamination, but it slightly affected the binding with the substrate. None of the mutant CDAs in Y33 showed enzymatic activity; they existed only as monomers, indicating that this residue, located at the intersubunit interface, may be responsible for the correct folding of human CDA. The insertion of an alanine instead of phenylalanine at position 137 led to a soluble but completely inactive enzyme unable to form a tetramer, suggesting that F137 residue may be important for the assembling of the tetramer and also for the arrangement of the CDA active site. Finally, R68G and R68Q mutations revealed that the presence of the amino group seems to be important for the catalytic process but not for substrate binding, as already shown in B. subtilis CDA. The quaternary structure of R68Q was not affected by the mutation, as shown by the SDS-induced dissociation experiments and CD studies, whereas R68G dissociated very easily in presence of small amounts of SDS. These experiments indicated that in the human CDA, the side chain of arginine 68 involved in the catalytic process in one subunit active site might come from another subunit. The data obtained from these studies confirmed the presence of a complicated set of intersubunit interactions in the active site of human CDA, as shown in other T-CDAs.

Cytidine deaminase (CDA) is a cytosolic metalloprotein whose functional unit can be either a homotetramer (T-CDA) or a homodimer (D-CDA), depending on the species. In 1994, the first crystal structure of the dimeric Escherichia coli CDA has been published. However, a crystal structure of a tetrameric CDA was not determined until 2002. Prior to the disclosure of the experimentally elucidated structure of a tetrameric CDA, we derived a homology model of the human T-CDA employing the crystal structure of the dimeric E. coli CDA as a template. The comparison of our theoretical model with the crystal structure of the human T-CDA, subsequently published in 2004, validates our prediction: not only of the structural features of the monomer and the details of the binding site, but also the multimeric arrangement of the subunits were determined with high accuracy in our model. By means of a phylogenetic analysis conducted on CDAs from various organisms, we demonstrate that the E. coli CDA is one of the furthest known homologues of the human enzyme. Nonetheless, despite the evolutionary distance and, more importantly, the different multimeric arrangement of their functional units, the E. coli CDA proved to have all the necessary information to accurately infer the structure of its human homologue.

Olive oil is the principal source of fats in the Mediterranean diet and it has been postulated that the components in olive oil can contribute to a lower incidence of coronary heart disease and cancers (prostate, colon, breast, and skin). The positive effects on human health can be attributed to the high level of phenolic compounds present in olive oil, the major ones being oleuropein, hydroxytyrosol and tyrosol. The aim of the present study was to evaluate the effect of oleuropein on enzymes involved in specific pathways of metabolism of proteins, carbohydrates and lipids. In particular, the effects of oleuropein on enzymes, such as trypsin, pepsin, lipase, glycerol dehydrogenase, glycerol-3-phosphate dehydrogenase, and glycerokinase, were investigated. Results demonstrate that oleuropein is able to activate pepsin and shows an inhibitory effect toward all the other enzymes tested, which suggests a new role for this polyphenol. In addition, a new method for lipase activity assay is presented.

In order to design new efficient cytidine based drugs, an intersubunit interactions study related to the active site has been performed on the wild-type cytidine deaminase (CDA) and on the mutant enzyme F137W/W113F. F137 is the homologous to the Bacillus subtilis CDA F125 involved in the subunit interactions. In presence of the dissociating agent SDS, wild-type human CDA dissociate into enzymatically inactive monomers without intermediate forms via a non-cooperative transition. Extensive dialysis or dilution of the inactivated monomers restores completely the activity. The presence of the strong human CDA competitive inhibitor 5-fluorozebularine disfavour dissociation of the tetramer into subunits in the wild-type CDA but not in mutant enzyme F137W/W113F.

Site-directed mutagenesis on human cytidine deaminase (CDA) was employed to mutate specifically two highly conserved phenylalanine residues, F36 and F137, to tryptophan; at the same time, the unique tryptophan residue present in the sequence at position 113 was mutated to phenylalanine. These double mutations were performed in order to have for each protein a single tryptophan signal for fluorescence studies relative to position 36 or 137. The mutant enzymes thus obtained, W113F, F36W/W113F and F137W/W113F, showed by circular dicroism and thermal stability an overall structure not greatly affected by the mutations. The titration of Trp residues by N-bromosuccinimide (NBS) suggested that residue W113 of the wild-type CDA and W36 of mutant F36W/W113F are buried in the tertiary structure of the enzyme, whereas the residue W137 of mutant F137W/W113F is located near the surface of the molecule. Kinetic experiments and equilibrium experiments with FZEB showed that the residue W113 seems not to be part of the active site of the enzyme whereas the Phe/Trp substitution in F36W/W113F and F137W/W113F mutant enzymes had a negative effect on substrate binding and catalysis, suggesting that F137 and F36 of the wild-type CDA are involved in a stabilizing interaction between ligand and enzyme.

The complementary DNA (cDNA) coding for Arabidopsis thaliana cytidine deaminase 1 (AT-CDA1) was obtained from the amplified A. thaliana cDNA expression library, provided by R. W. Davis (Stanford University, CA). AT-CDA1 cDNA was subcloned into the expression vector pTrc99-A and the protein, expressed in Escherichia coli following induction with isopropyl 1-thio-beta-d-galactopyranoside, showed high cytidine deaminase activity. The nucleotide sequence showed a 903-bp open reading frame encoding a polypeptide of 301 amino acids with a calculated molecular mass of 32,582. The deduced amino acid sequence of AT-CDA1 showed no transit peptide for targeting to the chloroplast or mitochondria indicating that this form of cytidine deaminase is probably expressed in the cytosol. The recombinant AT-CDA1 was purified to homogeneity by a heat treatment followed by an ion-exchange chromatography. The final enzyme preparation was >98% pure as judged by SDS-PAGE and showed a specific activity of 74 U/mg. The molecular mass of AT-CDA1 estimated by gel filtration was 63 kDa, indicating, in contrast to the other eukaryotic CDAs, that the enzyme is a dimer composed of two identical subunits. Inductively coupled plasma-optical emission spectroscopy analysis indicated that the enzyme contains 1 mol of zinc atom per mole of subunit. The kinetic properties of AT-CDA1 both toward the natural substrates and with analogs indicated that the catalytic mechanism of the plant enzyme is probably very similar to that of the human the E. coli enzymes.

Oocyte growth within the follicle is preponderantly due to the accumulation of hepatically derived yolk protein (vitellogenin, VTG) by receptor-mediated endocytosis; once in the oocyte, VTG is partially processed and stored in yolk globules. In some pelagic egg-laying marine teleosts, additional cleavages of yolk proteins followed by a pronounced water uptake occur concomitantly with final oocyte maturation. The aim of this study was to establish the lysosomal enzymes involved in these two proteolytic processes that characterize oocyte maturation of seabream Sparus aurata. The enzymatic activities of several cathepsins were assessed in the various classes of oocytes. Changes in cathepsin B, D, and L activity were found depending on the oocyte maturation stage; cathepsin B and D were found to be at maximum level in early-vitellogenesis oocytes, and cathepsin L in mid-vitellogenesis ones. Cathepsin D and L were purified from seabream ovary, and their roles in VTG and lipovitellin (LV) proteolysis, respectively, were analyzed. Here we demonstrate directly that one of the catalysts for the intraoocytic processing of VTG in yolk proteins is cathepsin D; however, we cannot exclude also a role of cathepsin B in the same process. On the other hand, cathepsin L is responsible for the second proteolytic cleavage of the LV components. We postulate that the acquisition of buoyancy by eggs through the hydration process may be regulated by enzymatic activation at the appropriate time of oocyte maturation, this process probably being the key event in the reproduction of this marine pelagic egg spawner.

The stereoselectivities of recombinant human deoxycytidine kinase (EC 2.7.1.74) (dCK) and of recombinant human cytidine deaminase (EC 3.5.4.5) (CDA) were investigated with respect to a series of cytidine analogs, most of them having the unnatural L-stereochemistry. The enantioselectivity of dCK was always low and generally favored the L-enantiomers in the case of beta-2',3'-dideoxycytidine (beta-ddC), 5-fluoro-beta-2',3'-dideoxycytidine (beta-FddC) and beta-cytidine (beta-riboC). Concerning beta-2'-deoxycytidine, dCK showed a preference for the D-enantiomer. All other examined beta-L-cytidine analogs, [1-beta-L-lyxofuranosyl cytosine (beta-L-lyxoC), l-beta-L-xylofuranosyl cytosine (beta-L-xyloC), and 5-fluoro-1-beta-L-xylofuranosyl cytosine (beta-L-Fxylo C)], were substrates of dCK regardless of the nature of the pentose. None of the studied alpha-L-anomers (alpha-L-riboC, alpha-L-araC, alpha-L-lyxoC, or alpha-L-xyloC) was a substrate of dCK. Contrasting with the relaxed enantioselectivity of dCK, CDA had a strict requirement for D-cytidine analogs since none of the already listed beta-L- or alpha-L analogs was a substrate or an inhibitor of the enzyme. The conjunction of the preceding stereochemical properties of dCK and CDA confers to L-cytidine analogs important potentialities in antiviral and anticancer therapies.

By site-directed mutagenesis on human cytidine deaminase (CDA), five mutant proteins were obtained: C65A, C99A, C102A, E67D and E67Q. The three cysteine mutants were completely inactive, whereas E67D and E67Q showed a specific activity about 200- and 200000-fold lower, respectively, than the wild-type CDA. Zinc analysis revealed that only E67D, E67Q and C65A contained 1 mol Zn2+/mol subunit as in the wild-type CDA. Kinetic measurements with the specific carboxylic group reagent N-ethoxy-carbonyl-2-ethoxy-1,2-dihydroquinoline performed on wild-type CDA suggest that Glu67 is essential for the catalytic process. Furthermore, when both native and denatured CDA was titrated with 5,5'-dithiobis(2-nitrobenzoic acid) six sulfhydryl groups were detected, whereas in the denatured and reduced enzyme nine such groups were found, according to the sequence data. When p-hydroxymercuriphenyl sulfonate was used, nine sulfhydryl groups were detectable and the release of 1 mol of zinc per mole of CDA subunit was revealed by the metal indicator dye 4-(2-pyridylazo)resorcinol. It seems plausible that the limiting step for the maintenance of zinc in the active site is the formation of coordination between Cys99 and Cys102, whereas Cys65 could lead the zinc to the correct position and orientation within the active site.

The immunohistochemical localization of carbonic anhydrase isoenzymes has never been investigated in avian renal tissue previously. Enzyme activity has largely been documented by histochemical and physiological reports. In this investigation, specific antisera were used to study the distribution of the cytosolic carbonic anhydrase II and III isoenzymes in the quail kidney. Comparison between the present findings and the corresponding histochemical patterns, previously obtained in the same species by a cobalt phosphate precipitation method, resulted in the bulk of renal carbonic anhydrase activity being attributed to the carbonic anhydrase II isoenzyme. Conversely, moderate carbonic anhydrase III immunostaining appeared to be confined to the smooth muscle cells of ureteral and arteriolar walls. Indirect evidence of the occurrence, in the quail kidney, of a membrane-associated carbonic anhydrase form, antigenically distinct from the II and III isoforms, was inferred.

Recent clinical studies have demonstrated that feeding with asses milk is a safe and valid treatment for infants affected by protein intolerance to dairy cows milk (Businco et al., 2000; Iacono et al., 1992). In fact, the composition of asses milk is similar to humans milk, especially concerning the lipid and protein fraction contents (Fantuz et al., 2001; Salimei et al., 2004). Furthermore, the protein fraction in asses milk is characterized by low casein and β-lactoglobulin content, probably responsible for the hypoallergenic characteristics of this milk, and by a quite high lysozime content (Fantuz et al., 2001; Salimei et al., 2004). In any case, there is not much information regarding the caseinic fractions of asses milk in the literature. Therefore, in the present study αS1and β-caseins were purified from asses milk by gel filtration chromatography followed by anion exchange chromatography on HPLC. The obtained caseins were characterized by SDS-PAGE and, after blotting on a PVDF membrane, were identified by N-terminal sequencing.

Donkey milk caseins display great microheterogeneity by two-dimensional electrophoresis (2-DE), probably because of a variable degree of phosphorylation and/or alternative splicing phenomena. In this work, we have investigated the complexity of the donkey milk caseins: The whole casein fraction was subjected to treatment with calf intestinal alkaline phosphatase to achieve dephosphorylation. The obtained apo forms were analyzed by 2-DE and compared with whole donkey caseins. As a result, donkey milk β-casein and its splicing variants are present as different phosphorylated isoforms, whereas α S1-casein displays several isoforms that are derived from both phosphorylation and glycosylation phenomena.

Cytidine deaminase (CDA), is one of the enzymes involved in the pyrimidine salvage pathways, which catalyzes the formation of uridine and deoxyuridine by the hydrolytic deamination of cytidine and deoxycytidine, respectively. Human CDA is a tetrameric enzyme of identical 15 kDa subunits, each containing an essential zinc atom in the active site. The substrate binds to each active site independently and the cooperativity between subunits has not been reported. CDA is able to recognize as substrates some antitumor and antiviral cytidine analogs rendering them pharmacologically inactive. In light of the role played by this enzyme, a deep knowledge of CDA active site and mechanism of catalysis is required. Site-directed mutagenesis, associated with molecular modeling studies, may be an important tool to discover the active site structure of an enzyme and consequently its mechanism of action. In this review are summarized the site-directed mutagenesis experiments performed on human CDA: through these studies it was possible to understand the role exerted by specific amino acid residues in CDA active site and in the contacts between subunits. The obtained results may open a way for designing new cytidine based drugs or more potent CDA inhibitors.

The purification procedure of NMN adenylyltransferase from bull testis presented here consists of a heat step and an acidic precipitation followed by four chromatographic steps, including dye ligand, adsorption and hydrophobic chromatography. The final enzyme preparation subjected to non-denaturing and denaturating PAGE with silver nitrate staining exhibited a single band. At this step the enzyme appeared to be homogeneous. The M(r) value of the native enzyme calculated by gel filtration was about 133,000. The protein appeared to possess a quaternary structure with four subunits of apparent M(r) 33,000 without disulphide interchain bonds. Isoelectric experiments gave a pI of 6.2, and pH studies showed the possible presence of an acidic group in the active site having a pKa of 4.9. Analysis of the amino acid composition showed the presence of more acidic residues than basic ones, according to the pI value calculated by Mono P FPLC. The Ea calculated by Arrhenius plot gave an apparent value of 55.7 kJ/mol. The Km values for NMN, ATP, NAD+ and PPi were 0.11, 0.023, 0.37 and 0.16 nM respectively. The polyclonal antiserum produced against the NMN adenylyltransferase reacted with the purified enzyme at different dilutions and recognized the enzyme in the homogenate as well.

In children with Cow Milk Protein Allergy (CMPA), when it is not possible to breast feed or to use cow milk, the clinical use of donkey milk is considered since several studies have demonstrated the high similarity of donkey milk compared to human milk. An analysis was performed on donkey milk protein profile by two-dimensional electrophoresis (2-DE) followed by N-terminal sequencing in order to give a panoramic view of the proteins that are present in donkey milk. Furthermore, the interest was focused on the casein fractions and on their phosphorylation degree that may influence the calcium binding ability of caseins. At this purpose experiments on donkey milk casein dephosphorylation have been performed and the dephosphorylated casein fractions have been identified after 2-DE analysis followed by N-terminal sequencing. Among caseins were found mainly αs1- and β-caseins that showed a considerable heterogeneity due to variable degree of phosphorylation and to the presence of genetic variants. Finally, a quantitative determination of some antimicrobial proteins, such as lactoferrin and lactoperoxidase, that could be able to stimulate the development of the neonatal intestine, was performed in donkey milk, with the results being 0.080±0.0035 g/L and 0.11±0.027 mg/L, respectively. From the obtained data is evinced that human and donkey milk contain considerable amounts of lysozyme and lactoferrin but lactoperoxidase is present only in small amounts, confirming the high similarity between donkey and human milk. The present study on donkey milk proteins may be useful to assess the nutritional characteristics of this milk that is used to feed children affected by CMPA, but also may open the possibility of utilizing donkey milk in the general population to benefit subjects with CMPA, such as adults and the elderly.

Cytidine deaminase (3.5.4.5, CDA), an enzyme of the pyrimidine salvage pathways, is responsible for the degradation and inactivation of several cytidine-based antitumoral drugs, such as cytarabine, gemcitabine, decitabine, and azacytidine. Thus, CDA inhibitors are highly sought after as compounds to be co-administered with said drugs in order to improve their effectiveness. Alternatively, the design of antitumoral drugs not susceptible to the action of CDA is also regarded as an attractive solution. Here, we describe a virtual screening for CDA ligands based on chemical similarity and molecular docking. The campaign led to identification of three novel inhibitors and one novel substrate, with a 19% hit rate, and allowed a significant extension of the structure-activity relationships, also in light of the compounds that resulted inactive. The most active compound identified through the screening was the inhibitor pseudoisocytidine, which has the potential to serve as a lead for highly stable compounds. The study also delineated the detrimental effect of 5-aza and 6-aza substitutions, the incompatibility of the presence of an amino group at the 3′-position, as well as the presence of very strict steric requirements around the 2′-arabino position and, even more, the N4-position. Importantly, these features can be exploited for the design of novel antineoplastic agents resistant to the action of CDA.

Cow milk protein allergy (CMPA) is an abnormal IgE-mediated reaction to cow milk proteins. Donkey’s milk could be considered suitable for feeding young children affected by severe IgE-mediated CMPA because its nutritional properties and composition are very close to human milk. Since donkey’s milk is available during a limited range of months during the year, it may be useful to find better storage conditions for this product. This study investigated the effects of the lyophilization treatment on donkey’s milk nutritional characteristics, and the results were compared with those obtained on fresh and frozen milk. Nutritional properties of lyophilized donkey’s milk remained basically unchanged compared with fresh milk. Two different probiotic strains were added to lyophilized donkey’s milk, and their viability was evaluated after milk reconstitution. The results obtained confirmed the possibility of producing a probiotic infant formula with beneficial properties using donkey’s milk as raw material.

The synthesis of 2′-deoxy and 2′,3′-dideoxy derivatives of 1-s-D-ribofuranosyl-1,3,4,7-tetrahydro-2H-1,3-diazepin-2-one (2) was undertaken in order to find new cytidine deaminase (CDA) inhibitors and potential adjuvants in anticancer chemotherapy. Replacement of ribose by a 2-deoxyribose moiety led to compound 9 that appeared slightly more potent than 2 (Ki = 2.5 × 10−8 M). Remarkably, the corresponding α-2′-deoxynucleoside 10 acted as a very potent inhibitor of human placenta CDA, with a Ki = 7.5 × 10−8 M. Attempt to synthesize the 2′,3′-dideoxy derivative of 2 led to N-[4,5-dihydroxy-1-(2-oxo-2,3,4,7-tetrahydro[1,3] diazepin-1-yl)-pentyl]-2,2,2-trifluoroacetamide (13), which is devoid of CDA inhibitory activity.

Publisher Summary Since antiquity, oil obtained from the fruit of the olive ( Olea europaea ) has been valued for its many medical properties. Peoples as ancient as the Egyptians have recognized the medical benefits and food-preservation properties of olives, olive oil, and olive leaf extracts. Since the 1800s, the bitter component in olives has been used in humans against malaria-induced fevers, and beginning in the last century, researchers have focused considerable attention on the health benefits of the various components of olive oil. In particular, many studies have assigned to polyphenols, the minor components of olive oil, the healthy effects observed. Oleuropein, one of the major polyphenols present in olive oil, possesses antimicrobial, antiviral, and antifungal properties. In addition, further studies reported that it is a powerful antioxidant as well as a hypotensive and hypoglycemic agent. Oleuropein exerts protective effects against heart disease and cancers. Other studies have demonstrated that oleuropein and its two main metabolites (hydroxytyrosol and elenoic acid) are completely non-toxic in several animal species and do not interfere with normal embryonic development. Knowing that oleuropein is a non-toxic compound with healthy properties, this chapter investigates its possible role as metabolism modulator. For this reason, it determines the in vitro effects of oleuropein on enzymes involved in proteic, glucydic, and lipidic metabolism. The results obtained from these studies are summarized.

In the present work the effect of a mutation on tyrosine 33 residue (Y33G) of human cytidine deaminase (CDA) was investigated with regard to protein solubility and specific activity. Osmolytes and CDA ligands were used to increase the yield and the specific activity of the protein. The mutant enzyme was purified and subjected to a kinetic characterization and to stability studies. These investigations reinforced the hypothesis that in human CDA the side chain of Y33 is involved in intersubunit interactions with four glutamate residues (E108) forming a double latch that connects each of the two pairs of monomers of the tetrameric CDA.

We report the kinetics and molecular properties of CD38 purified from bovine lung microsomal membranes after its solubilization with Triton X-100. The enzyme was found to be a novel member of a multicatalytic NAD+-glycohydrolase (NADase, EC 3.2.2.6). It was able to utilize NAD + in different ways, producing nicotinamide (Nam) and either adenosine diphosphoribose (ADPR, NADase activity) or cyclic ADPR (cADPR, cyclase activity); it also catalyzed the hydrolysis of cADPR to ADPR (cADPR, hydrolase activity). In addition, the enzyme catalyzed the pyridine base exchange reaction with conversion of NAD + into NAD analogues. These data are evidence that CD38 is involved in the regulation of both NAD+ and calcium-mobilizing agents, the concentration resulting in an essential enzyme that plays a key role in cellular energy and signal-transduction systems.

Protein fraction characterization of sheep milk from the Comisana breed S. Vincenzetti & P. Polidori & P. Mariani & A. Vita Published online: 7 August 2008 # Springer Science + Business Media B.V. 2008

We have previously reported for the first time the purification to homogeneity of the enzyme NMN adenylyltransferase (EC 2.7.7.1) from yeast and its major molecular and catalytic properties. The homogeneous enzyme was found to be a glycoprotein containing 2% carbohydrate and 1 mol of adenine residue and 2 mol of phosphate covalently bound per mole of protein. Such a stoichiometry, apparently consistent with that of ADP-ribose, prompted us to further investigate the possibility that NMN adenylyltransferase could be subjected to poly(ADP-ribosylation) in vitro in a reconstituted system. Poly(ADP-ribose) polymerase was purified to homogeneity from bull testis by means of a rapid procedure involving two batchwise steps on DNA-agarose and Reactive Blue 2 cross-linked agarose and a column affinity chromatography step on 3-aminobenzamide-Sepharose; the optimal conditions for the poly(ADP-ribosylation) of exogenous substrates were determined. When pure NMN adenylyltransferase was incubated in the presence of the homogeneous poly(ADP-ribose) polymerase, a marked inhibition of the polymerase was observed, both in the presence and in the absence of histones, while the activity of NMN adenylyltransferase was not affected. The inhibition could not be prevented by increasing the concentrations of either DNA or NAD. Mg2+ did not affect the activity or the inhibition. The significance of such a phenomenon is at present unknown, but it may be of biological relevance in view of the close topological and metabolic relationship between the two enzymes.

The thermal stability of human cytidine deaminase (CDA), an enzyme involved in pyrimidine metabolism was investigated. With this in view, the residues R68 and Y60, supposed to be involved in the intersubunit interactions and in the catalytic site of CDA, were mutated to glutamine and glycine, respectively. Thermal stability experiments were performed on the purified mutants by means of circular dichroism and enzymatic assays. The results obtained should be useful for designing more efficient cytidine based drugs for chemotherapy.

S. Petrini1,∗, M. Ferrari1, S. Vincenzetti2, A. Vita2, A. Amici3 and G. Ramadori3 1Istituto Zooprofilattico Sperimentale della Lombardia e dell’Emilia-Romagna, 7/9, 25124 Brescia, Italy; 2Department of Veterinary Sciences, Section of Biochemistry, Faculty of Veterinary Medicine, University of Camerino, 62024 Matelica, Italy; 3Department of Molecular Cell and Animal Biology, Laboratory of Genetic Immunization, Faculty of Biology, University of Camerino, 62032 Camerino, Italy ∗Correspondence: E-mail: stefano petrini1@virgilio.it

In the recent years the interest around donkey’s milk had a marked increase since it has been demonstrated that this milk can be used for feeding of infants affected by dairy cow’s milk protein intolerance (Businco et al., 2000; Iacono et al., 1992).

Although DNA vaccines have several advantages over conventional vaccines, antibody production and protection are often not adequate, particularly in single plasmid vaccine formulations. Here we assessed the potential for a combined vaccine based on plasmids encoding the membrane-anchored or secreted forms of bovine herpesvirus type 1 (BHV-1) glycoprotein B and D (gB and gD) to induce neutralizing and cell mediated immune responses in mice. Animals were injected by intramuscular, subcutaneous and intranasal routes. Mice immunized with the combined vaccine containing the secreted forms of BHV-1 glycoproteins developed higher titers of anti-BHV-1 neutralizing antibodies, compared to wild type gB/gD combined plasmids and to single plasmid injected groups. Cellular immunity was also developed in mice immunized with combined vaccines, whereas low or no response were observed in single plasmid injected animals. The data suggest the potential use of this combined vaccine in in vivo trials of calves, in order to evaluate its protective efficacy.

An intersubunit interactions study related to the active site has been performed on the wild-type cytidine deaminase (CDA) and on the mutant enzyme F137W/W113F. F137 is the homologous to the Bacillus subtilis CDA F125 involved in the subunit interactions. In the presence of SDS, wild-type human CDA dissociates into enzymatically inactive monomers without intermediate forms via a non-cooperative transition. Extensive dialysis or dilution of the inactivated monomers restores completely the activity. Circular dichroism measurements show that the secondary/tertiary structure organization of each subunit is unaffected by the SDS concentration, while the mutation Phe/Trp causes weakening in quaternary structure. The presence of the strong human CDA competitive inhibitor 5-fluorozebularine disfavours dissociation of the tetramer into subunits in the wild-type CDA, but not in mutant enzyme F137W/W113F. The absence of tyrosine fluorescence and the much higher quantum yield of the double mutant protein spectrum suggest the occurrence of an energy transfer effect between the protein subunits. This assumption is confirmed by the crystallographic studies on B.subtilis in which it is shown that three different subunits concur with the formation of each of the four active sites and that F125, homologous to the human CDA F137, is located at the interface between two different subunits contributing to the formation of active site.

Cytidine deaminase (CDA) purified from human placenta revealed the presence of five isoenzymatic forms that differ only in their isoelectric point. Since human cytidine deaminase exists in two variants (CDA 1 and CDA 2) with a non-conservative amino acid substitution at codon 27, in this work we demonstrate that these two variants may combine together in vitro, giving five CDA isoforms as observed in vivo from human placenta. For this purpose, each of the two forms of CDA was purified close to homogeneity and dissociated into monomers in the presence of a small amount of sodium dodecyl sulfate as a dissociating agent. The monomers were mixed together and subjected to anion-exchange chromatography and to chromatofocusing analysis in order to visualize the formation of the five isoforms. Furthermore, for both CDA 1 and CDA 2 some substrates and inhibitors of CDA were assayed, with the aim of demonstrating different kinetic behavior between the two natural variants.

In the absence of an experimentally elucidated three-dimensional structure of the human CDA, we built an homology model of this enzyme starting from the crystal structure of its E. coli homologous. Furthermore, we docked in the active site alternatively the substrate, the intermediate or the product. By means of molecular dynamics simulations, we determined the topology of the active site, identifying the amino acids involved in the catalytic mechanism, and outlining the central role played by E67.

N6-Cycloalkyl-2',3'-dideoxyadenosine derivatives and (2-chloro)-N6-cycloheptyl-3-deazaadenosine have been synthesized and tested, along with other (deaza)purine (deoxy)nucleosides from our chemical library, as inhibitors of virus replication against Bovine Herpes Virus 1 (BHV-1) and sheep Maedi/Visna Virus (MVV). Most compounds demonstrated good antireplicative activity against MVV, showing also low cell toxicity.

A series of N(6)-cycloalkyl-2',3'-dideoxyadenosine derivatives has been prepared by coupling of 2,6-dichloropurine to protected 2,3-dideoxyribose, followed by reaction with appropriate cycloalkylamines. Synthesized compounds, along with other purine nucleoside analogues previously synthesized in our laboratory, have been tested for their antiviral activity against Bovine herpesvirus 1 (BHV-1) and sheep Maedi/Visna Virus (MVV), the latter being an in vitro and in vivo model of Human Immunodeficiency Virus (HIV). All compounds showed good antireplicative activity against MVV, with the N(6)-cycloheptyl-2',3'-dideoxyadenosine (5b) being the most active [effective concentration (EC(50)) causing 50% reduction of cytopatic effects (CPE)=27 nM]. All compounds showed also a from low to very low cell toxicity, resulting in a cytotoxic dose 50 (CD(50))/EC(50) ratio in some cases higher than 1000.

2'-Deoxy-beta-L-5-azacytidine(L-Decitabine), beta-L-5-azacytidine, and derivatives were stereospecifically prepared starting from L-ribose or L-xylose. D- and L-enantiomers of 2'-deoxy-beta-5-azacytidine were weak substrates of human recombinant deoxycytidine kinase (dCK), whereas both enantiomers of beta-5-azacytidine or the L-xylo-analogues were not substrates of the enzyme. None of the reported derivatives of beta-L-5-azacytidine was a substrate of human recombinant cytidine deaminase (CDA).

Although 2′-deoxy-β- d -5-azacytidine (Decitabine) and β- d -5-azacytidine display potent antileukemic properties, their therapeutic use is hampered by their sensitivity to nucleophiles and to deamination catalysed by cytidine deaminase. As shown earlier [Shafiee M., Griffon J.-F., Gosselin G., Cambi A., Vincenzetti S., Vita A., Erikson S., Imbach J.-L., Maury G., Biochem. Pharmacol. 56 (1998) 1237–1242], β- l -enantiomers of cytidine derivatives are resistant to cytidine deaminase. We thus synthesized several 5-azacytosine β- l -nucleoside analogues to evaluate their enzymatic and biological properties. 2′-Deoxy-β- l -5-azacytidine ( l -Decitabine), β- l -5-azacytidine, 1-(β- l -xylo-furanosyl)5-azacytosine, and 1-(2-deoxy-β- l -threo-pentofuranosyl)5-azacytosine were stereospecifically prepared starting from l -ribose and l -xylose. d - and l -enantiomers of 2′-deoxy-β-5-azacytidine were weak substrates of human recombinant deoxycytidine kinase (dCK) compared to β- d -deoxycytidine, whereas both enantiomers of β-5-azacytidine or the l -xylo-analogues were not substrates of the enzyme. As expected, none of the presently reported derivatives of β- l -5-azacytidine was a substrate of human recombinant cytidine deaminase (CDA). The prepared compounds were tested for their activity against HIV and HBV and they did not show any significant activity or cytotoxicity. In the case of l -Decitabine, this suggests that the enantioselectivities of concerned enzymes other than dCK and CDA might not be favourable.

Although 2′-deoxy-β- d -5-azacytidine (Decitabine) and β- d -5-azacytidine display potent antileukemic properties, their therapeutic use is hampered by their sensitivity to nucleophiles and to deamination catalysed by cytidine deaminase. As shown earlier [Shafiee M., Griffon J.-F., Gosselin G., Cambi A., Vincenzetti S., Vita A., Erikson S., Imbach J.-L., Maury G., Biochem. Pharmacol. 56 (1998) 1237–1242], β- l -enantiomers of cytidine derivatives are resistant to cytidine deaminase. We thus synthesized several 5-azacytosine β- l -nucleoside analogues to evaluate their enzymatic and biological properties. 2′-Deoxy-β- l -5-azacytidine ( l -Decitabine), β- l -5-azacytidine, 1-(β- l -xylo-furanosyl)5-azacytosine, and 1-(2-deoxy-β- l -threo-pentofuranosyl)5-azacytosine were stereospecifically prepared starting from l -ribose and l -xylose. d - and l -enantiomers of 2′-deoxy-β-5-azacytidine were weak substrates of human recombinant deoxycytidine kinase (dCK) compared to β- d -deoxycytidine, whereas both enantiomers of β-5-azacytidine or the l -xylo-analogues were not substrates of the enzyme. As expected, none of the presently reported derivatives of β- l -5-azacytidine was a substrate of human recombinant cytidine deaminase (CDA). The prepared compounds were tested for their activity against HIV and HBV and they did not show any significant activity or cytotoxicity. In the case of l -Decitabine, this suggests that the enantioselectivities of concerned enzymes other than dCK and CDA might not be favourable.

A series of β- d - and β- l -cytidine analogues were evaluated for their inhibitory effect on the replication of maedi-visna virus (MVV) strains KV1772 and MV1514 cultured on sheep choroid plexus cells and the sheep chondrocyte cell line G81092, respectively. Eleven cytidine analogues were selected for the anti-viral test. Five of them belong to the family of the 2′,3′-dideoxycytidine analogues, well known for their activity against human immunodeficiency virus (HIV). The others, all newly synthesized, were potential anti-viral and/or anti-leukemic agents. None of the compounds under study had a toxic effect in both anti-viral assay systems up to a 300 μM concentration. Based on the cytopathic effects (CPE), the virus replication was completely inhibited by the five 2′,3′-dideoxycytidine analogues at a concentration of 50 μM, whereas the others six newly synthesized compounds induced titre reductions of 4–5 log units. The effective concentration causing 50% reduction of CPE (EC 50 ) was of 5 μM for the five 2′,3′-dideooxycytidine analogues and for β- l -XyloFc, whereas the value of 50 μM was found for the b- l -XyloC and the four 5-azacytidine compounds tested. All these data reveal a good correlation between inhibition of MVV replication by several nucleoside cytidine analogues and their reported anti-HIV activity.

Human cytidine deaminase (CDA, EC 3.5.4.5) is a tetramer of identical subunits (16KDa/subunit) each containing a single zinc atom1 and catalyzes the deamination of cytidine (CR) and deoxycytidine (CdR) to their corresponding uracil compounds. Several cytosine-based drugs, such as cytosine arabinoside and 5-Aza-CdR,2 which are anti-tumor agents used in the chemotherapy, are also deaminated by CDA. Thereby they loose their pharmacological properties. The deamination mechanism of CDA is similar to that of adenosine deaminase (ADA)3,4 and consists of an enzyme-assisted direct water attack on the nucleoside C-4 and C-6 carbon atoms, respectively. In both enzymes the hydroxyl group thus formed interacts with an active-site zinc atom and a negatively charged carboxylate group. The amino acid sequences of ADA and CDA are unrelated, except for a short sequence within the active site: in Escherichia coli these sequences are TVHAE and TVHAGE for CDA and ADA, respectively5 and the H residue is involved in zinc coordination in both deaminases. The E residue participates to the catalytic mechanism of CDA,3 whereas in the crystal structure of ADA4 the glutamic residue is shown to share a proton with N-l of the purine ring, while an aspartic residue (D 295) plays the same role as the glutamate in CDA, suggesting the importance of the presence of a carboxyl group in the catalytic site of nucleotide deaminases. In fact, in both the human and the Bacillus subtilis CDA the E residue is conserved, whereas the H residue is replaced by a C residue. In the present paper we demonstrate the importance of the Glu-67 carboxylic group by studying the effect on enzyme activity of reacting wild-type CDA with the specific carboxyl reagent N-ethoxy- carbonyl-2-ethoxy-l,2-dihydroquinoline (EEDQ), and by analyzing two mutant enzymes in which Glu-67 has been replaced with Asp and Gln (E67D and E67Q), respectively.

The three-dimensional structure of homodimeric E. coli cytidine deaminase (CDA)1 showed a zinc atom coordinated to histidine (H 102) and two cysteine residues (C 129 and C 132) in the active site. The role of zinc in catalysis is to bind and activate a water molecule for attack on the pyrimidine ring with consequent elimination of ammonia. The human CDA cDNA has been cloned and the protein expressed in E. coli is a tetramer composed of identical 16.2 KDa subunits each containing a firmly bound zinc atom in the active site.2 Comparison of the deduced amino acid sequence of the human recombinant CDA with that of E. coli enzyme1 identified the putative zinc coordinating residues as C99, C 102 and C65, the latter replacing H102 of the E. coli enzyme. To confirm the proposed role of the three indicated cysteines in catalysis of human CDA, we have studied the effect of specific thiolic reagents, and we have constructed and characterized three mutant proteins by site directed mutagenesis in which each of the cysteines, C99, C102 and C65 were replaced by an alanine residue.