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Tryptic and chymotryptic digestion of peptide B, the N-terminal fragment obtained by cyanogen bromide cleavage of thioredoxin, provided the information required to determine the contiguity of the peptic fragments studied previously. The complete sequence of the 37 residues of peptide B could thus be established. Peptide B contains the active center of thioredoxin. Its amino acid sequence was found to be: -Trp-Ala-Glu-Trp-Cys-Gly-Pro-Cys-Lys-Met-. This sequence supports earlier conclusions dragon from fluorescence studies of thioredoxin, which indica ted a close relationship between one or both tryptophan residues and the disulfide bridge of the active site. Peptide maps of the tryptic digests of carboxymethylated thioredoxin and of the two cyanogen bromide fragments are described. Amide nitrogen analyses of thioredoxin and the two cyanogen bromide fragments demonstrate that all seven amide groups of thioredoxin are localized in the C-terminal fragment (peptide A). [ABSTRACT FROM AUTHOR]

Peptide studies on two acidic proteins, A1 and A2, from 50-S ribosomes of Escherichia coli indicate a closely related primary structure. 1. Amino acid compositions of the tryptic peptides of the two proteins are identical, with exception of the amino terminal peptide. 2. The N-terminal amino acid sequence of A2-protein is Ser-Ile-Thr-Lys, while that of A1-protein is N-acetyl-Ser-Ile-Thr-Lys. 3. The estimated number of 120 amino acid residues in each polypeptide chain is consistent with the physical molecular weight estimate. 4. In 50% of the polypeptide chains, in both A1- or A2-protein, a specific lysine residue is replaced by ε-N-monomethyl-lysine. [ABSTRACT FROM AUTHOR]

1. The arginine-requiring mutant of Chlamydomonas reinhardi, isolated by Ebersold in 1956 and called arg-1, shows no activity of the enzyme acetyl-glutamate-reductase, for this reason we propose to call this mutant arg C1. By analogy with this we call the arginine-requiring mutant arg-2, isolated by Eversole in 1956, arg G2. 2. Under circumstances in which the synthesis of the last enzyme of the arginine pathway, the argininosuccinate lyase, shows strong repression and derepression, we could not find any regulation of the synthesis of the 2nd up to and including the 6th enzyme of this pathway. 3. A more detailed study on the 6th enzyme of the pathway, the ornithine transcarbamylase, also failed to show any regulation of the synthesis. The findings of 2 and 3 support our hypothesis on the regulation of the arginine biosynthesis in Chl. Reinhardi, which we presented in the preceding paper. [ABSTRACT FROM AUTHOR]

The sequences of the 119 amino acids of bovine and porcine luteinizing hormone β-subunits were determined, 17 amino acid replacements being observed between these species. Variability in the primary structure was observed for porcine β-subunit, in that position 10 is occupied by both arginyl and glutamyl residues. No free amino terminal residue was detected for both porcine and bovine β-polypeptide chains and both exhibited carboxy-terminal heterogeneity. The homology of the β-subunits of luteinizing hormone from various species and the β-subunit of the bovine thyroid-stimulating hormone is discussed as the subunit of both hormones can combine with a similar α-subunit. [ABSTRACT FROM AUTHOR]

The primary structure of porcine luteinizing hormone α-subunit was established by determination of the amino acid sequence of its tryptic peptides, which were aligned by homology with the known sequence of ovine luteinizing hormone α-subunit. Its polypeptide chain is shorter by six amino acid residues at its amino-terminus, when compared to the ovine α-subunit. Furthermore four amino acid replacements are observed in the porcine as compared with the ovine chain. Heterogeneity of both carbohydrate prosthetic groups of porcine luteinizing hormone α-subunit is indicated by the different sugar compositions of the glycopeptides isolated in the course of this work. [ABSTRACT FROM AUTHOR]

The biosynthesis of melittin, the main toxin of bee venom, was studied in vivo by feeding radioactive amino acids to honey bees. Extracts from venom glands were analyzed for the presence of labeled melittin and other components. Radioactivity was first incorporated into another peptide which is considered to be a precursor of melittin. This conclusion is based on the observed labeling kinetics demonstrating the transient formation of this peptide. Furthermore, the structural similarity between melittin and this component could be established. Evidence is presented showing that it differs from melittin at the amino end. The precursor peptide could not be detected in the ejected venom. [ABSTRACT FROM AUTHOR]

Amino acid analyses of L-lactate dehydrogenase from baker's show that the minimum molecular weight (53 000 daltons) of the protein is much lower than found in the literature (80 000). This result, combined with those reported in the following papers, leads to a revision of the dimeric model generally accepted for cytochrome b2 [ABSTRACT FROM AUTHOR]

An investigation has been made of the acid soluble protein fractions of wool that has been reduced with benzylmercaptane and treated with methyliodide. When this modified wool was shaken in dilute formic acid (50 v/v) at room temperature for 1 hour, 7% of a protein material was dissolved. After dialysis and subsequent lyophylisation the protein material was isolated, and shown to be heterogeneous by paper electrophoresis. Fractionation of this protein on Sephadex G-75 in dilute acetic acid gave more than six components of relatively high content of tyrosine and phenylalanine. One of these fractions, obtained in good yield, was purified by rechromatography. For further separation the protein fraction was subjected to ion exchange chromatography on Dowex 1 (×2) columns. By stepwise elution with buffers of decreasing pH-values, containing acetic acid and 8 M urea, four subfractions were obtained. The amino acid compositions of reduced wool, of the protein obtained by formic acid extraction, of the fraction after gel filtration on Sephadex G-75 and of one subfraction on Dowex 1 (×2) are given. In all three fractions an increase in glycine, tyrosine and phenylalanine content was observed with relatively low amounts of basic and acidic amino acids. The subfraction obtained after the final step of separation on Dowex 1 (×2) was further characterised by endgroup determinations. Dnp­glycine was the only N-terminal amino acid with traces of Dnp­alanine as contaminant. Hydrazinolysis resulted in tyrosine on the C-terminus. After digestion of the subfraction by trypsin and chymotrypsin a number of peptides with different chain lengths was obtained, indicating that, tyrosyl residues had accumulated and that larger arginyl­peptides were present. Sedimentation measurements by ultracentrifugation indicated that the subfraction had a weight average of apparent molecular weight in the range of 9,000 to 13,000. This is in agreement with the molecular weight of 16,400 derived from the amount of Dnp­glycine and the calculated one from the amino acid composition. The analytical results show that the subfraction represents a single polypeptide chain containing only one N-terminal residue and about hundred aminoacids of which about fifty are glycine, tyrosine and phenylalanine. [ABSTRACT FROM AUTHOR]

The present paper describes the effect of (+)-biotin on the metabolism of a freshly isolated strain of Desulphovibrio desulphuricans. In proliferating pure cultures of this Zürich strain on a synthetic substrate with ammonium chloride, lactate and sulphate an oxido-reduction process takes place according to the stoichiometric relation established by Baars (1930). In the medium mentioned (+)-biotin was shown to have favourable action when added in comparatively small amounts, whereas in presence of greater amounts of the vitamin a marked inhibition was observed. The maximum stimulation is induced at a concentration of 25 jig. of biotin per litre, while a pronounced inhibition sets in when the vitamin concentration is increased from 100 to 250 μg. per litre. It is proposed that the beneficial effect of biotin might be related to the action of the vitamin in the synthesis of aspartic acid and other amino acids from pyruvic acid, carbon dioxide and ammonia through Wood-Werkman condensation, amination and transamination. [ABSTRACT FROM AUTHOR]

The study of the structure of the peptides arising from native, oxidized or reduced and maleinized bovine growth hormone on incubation with trypsin, ehymotrypsin and pepsin is reported. The data obtained permitted the assembly of a unique sequence of amino acids for the poly-peptide chain of the protein. Various corrections and one addition to the sequence previously communicated are made. [ABSTRACT FROM AUTHOR]

The amino-acid sequence of the Fe fragment of a mouse monoclonal IgG2a molecule is presented. With the exception of one deletion, this region possesses the same length as that of the human γl chain or that of the rabbit γ chain. Identities between the Fc fragments of 3 animal species (human, mouse and rabbit) average 50% and are markedly more pronounced for the CH2 domain than for the CH3 domain, observation which is in agreement with an independent evolution of each homology region. Strikingly, the degree of conservation of the VH region is of the same order of magnitude as that observed for the Fc fragment. This parallelism in evolution is discussed. [ABSTRACT FROM AUTHOR]

When cultures of biotin-requiring mutant of Brevibacterium divaricatum NRRL-2311 were treated in early logarithmic phase with penicillin (2–3 units/ml) in a glucose-mineral medium under excess supply of biotin, large amounts of a high-molecular-weight material accumulated in the medium. The phenomenon could not be observed with cultures run in parallel from which penicillin was omitted. Chemical analyses of the excreted material isolated from the media of 1-h and 24-h penicillin-treated cultures, showed that the main constituents were peptidoglycan components of noncross-linked structure bearing both L- and D-alanine residues: evidence was also obtained for the occurrence of extractable lipid material, non-amino sugars and organic phosphate. Under identical conditions, the excretion of peptidoglycan could be induced by ampicillin and cloxacillin, respectively, but not by bacitracin. Addition of penicillin to biotin-requiring mutant of M. glutamicus yielded similar results, indicating that the phenomenon was not restricted to the Brev. divaricatum strain. This suggests that excretion of peptidoglycan material by the two biotin-requiring mutants might be the result of two events, (a) a change in the osmotic barrier of the cell and (b) specific inhibition of cross-link formation in peptidoglycan induced by penicillin. Several procedures were examined for the isolation and purification of the peptidoglycan complex excreted by penicillin-treated Brev. mutant. Suitable labelling experiments with L-[U-14C]glutamic acid and analyses of lysozyme digests of the purified fractions, suggest that some of the components might contain murein fragments covalently linked to a polysaccharide portion. [ABSTRACT FROM AUTHOR]

The venom of Naja melanoleuca has Been fractionated, first on Sephadex G-50 and the most toxic fraction (judged by the LD50 determined in mice) has been further fractionated on SESephadex C2.5 at two pH values. Six polypeptide fractions showing single N-terminal ammo acid residues have been isolated in quantities sufficient for sequence determination. Of these, all but one are neurotoxins. Three, are "long" toxins which are identical up to the 20th residue and can be identified with the "long" toxin, b, already characterized by other workers. A fourth is a "short" toxin, identifiable with toxin d also previously described. The fifth neurotoxic component is different from all eomponents of the venom previously described. It is a "long" toxin, the primary sequence of which has been determined unambiguously, which resembles α-bungarotoxin more closely than do any other "long" toxins. [ABSTRACT FROM AUTHOR]

The gycine-rich, arginine-rich histone from calf thymus contains 102 residues of amino acids, distributed as follows: Asp5, Thr7, Ser2, Glu6, Pro1, Gly17,. Ala7, Val9, Met1, Ile6, Leu8, Tyr4, Phe2, Lys10, Lys(Me)1, His2, Arg14. From a tryptic hydrolysate of Gly- and Arg-rich histone, 18 peptides were isolated by fractionation on a column of Chromobeads P followed by purification by paper electrophoresis and chromatography. The amino acid compositions of these peptides are reported. The sequence of 12 of these tryptic peptides has been established. The amino-terminal tryptic peptide is Ac-Ser-Gly-Arg. The carboxylterminal tryptic peptide is Thr-Leu-Tyr-Gly-Phe-Gly-GlyCOOH. [ABSTRACT FROM AUTHOR]

Amino acid analyses of L-lactate dehydrogenase from baker's show that the minimum molecular weight (53 000 daltons) of the protein is much lower than found in the literature (80 000). This result, combined with those reported in the following papers, leads to a revision of the dimeric model generally accepted for cytochrome b2 [ABSTRACT FROM AUTHOR]

By mild treatment of tRNAyeastPhe with acid (pH 2.9, 37°, 3–4 hours) the base Y+, which according to RajBhandary, Khorana et al. is located right next to the anticodon, can be excised without breaking the chain. Y+ and the acid treated tRNAPhe (=tRNAHClPhe) were characterized and the conversion of tRNAPhe to tRNAHClPhe was investigated in detail. Y+ is a rather hydrophobic compound of unknown structure. Y+ and ribose were found when the nucleoside Y was treated with acid. Some physical and chemical properties of Y+ are reported. Y+ can be isolated easily in pure form from oligonucleotides, tRNAyeastPhe, or even unfractionated tRNAyeast (not tRNAcolt) by mild acid treatment and subsequent extraction into chloroform. tRNAHClPhe and tRNAPhe have very similar molecular sizes and shapes since their Sephadex elution profiles were overlapping. The facile separation of tRNAPhe and tRNAHClPhe by countercurrent distribution, on columns of methylated albumin on Kieselgur or benzoylated DEAE­cellulose is due, at least in part, to the removal of a hydrophobic residue from an exposed region of the tRNAPhe. tRNAHClPhe can be charged with Phe to the same extent as tRNAPhe. Since also the Michaelis constant of phenylalanyl tRNA synthetase is the same for both tRNAs (1.5 × 10-7 M) and the maximal velocity of charging is decreased by only one third in tRNAHClPhe, it can be concluded, that Y and probably the whole anticodon loop are not essential parts of the synthetase recognition region of tRNAPhe in homologous charging reactions. It was found that tRNAHClPhe and tRNAPhe from which the —CpCpA endgroups had been removed do not differ in their acceptor capacities for CTP and ATP. In the ribosome systems, Phe-tRNAHClPhe does not bind to poly (U) or other polynucleotides and does not transfer its amino acid onto growing peptide chains. The complete loss of codon recognition is attributed largely to a change in the conformation of the anticodon loop. The ultraviolet spectra of an Y-containing hexanucleotide and of its acid conversion products are in agreement with the notion of a strong interaction between Y+ and its neighbouring bases, as are the rate differences in the liberation of Y+ from Y [1.5 times faster] and the hexanucleotide, respectively. The rate of tRNAHClPhe formation, as measured by methylated albumin on Kieselgur­column chromatography and binding assays, is the same as the rate of Y+-liberation from the hexa­nucleotide. The acid induced conversion of tRNAPhe to tRNAHClPhe is a completely selective reaction affecting Y as the only nucleoside of tRNAPhe. [ABSTRACT FROM AUTHOR]

Four fractions of tRNASer aggregates were separated from tRNASer by chromatography on Sephadex G-100. They are eluted from the column in positions different from those of native, denatured and amino acid charged tRNASer. According to their sedimentation coefficients, two of the aggregate fractions contain tRNASer dimers, whereas the two other fractions consist of higher aggregates. [ABSTRACT FROM AUTHOR]

Isolated cyanogen bromide fragments of the αB2 chain of α-crystallin contained 67 and 107 residues. respectively. Part of the sequence of the C-terminal fragment was elucidated by Edman and Begg sequenator analysis. Sequences of the tryptic peptides were determined by a combination of various Edman degradation techniques. Overlaps of tryptic peptides were established by selective modification of lysine residues and subsequent tryptic cleavage and by isolation of peptides after hydrolysis with chymotrypsin, thermolysin and a staphylococcal protease. The sequence of the αB2 chain comprises 175 residues corresponding to a molecular weight of 20070. This value is somewhat lower than that assumed hitherto. A high degree of homology between the αB2 and the αA2 chain, the major polypeptides, of bovine α-crystallin was observed. [ABSTRACT FROM AUTHOR]

The phosphofructokinase of the red cells of rats is exquisitely sensitive to inhibition by ATP. The apparent Ki for ATP is decreased with lower pH values and fructose-6-phosphate concentrations. 2,3-Bisphophoglycerate, which is present in the red cells of man and many mammals, inhibits the phosphofructokinase in a synergistic manner with ATP. The inhibitory effect of phosphoenolpyruvate is biologically insignificant. It may be estimated that the enzyme would be practically completely inactive under cellular conditions without the action of positive effectors. There exist a multitude of positive effectors. Significant activations under cellular conditions are exercised by AMP, glucose 1,6-bisphosphate and inorganic phosphate. Fructose 1,6-bisphosphate activates to a limited extent and ADP only at alkaline pH values. All positive effectors produce a decreased inhibition by ATP and increased affinity of the enzyme for fructose 6-phosphate. AMP is the activator with the highest affinity, while glucose 1,6-bisphosphate may be considered as a baseline activator owing to its sluggish turnover. The data may be fitted in a qualitative manner to the model of Monod, Wyman and Changeux. It is possible that the negative anionic effectors act on the same site. [ABSTRACT FROM AUTHOR]

1. Ancrod is inactivated by diisopropyl [32P]phosphofluoridate when one g-atom of 32P is irreversibly bound to 34600 g enzyme. 2. Acid hydrolyis of the radioactive and inactive enzyme confirms that the label is attached to a serine residue in L-serine-O-[32P]phosphate. 3. Ancrod is inactivated by the substrate analogue α-N-(nitrobenzyloxycarbonyl)-L-arginyl chloromethyl ketone. Kinetic analysis shows that the irreversible inactivation is preceded by a reversible binding of inactivator to the enzyme. This inactivation is prevented by the addition of α-N-benzoyl-L-arginine ethyl ester. 4. The rate of inactivation of ancrod by the active-site-directed reagent depends on the ionisation of a group with pK(app) of 7.4. This group is probably the histidine residue which is lost when the enzyme is inactivated by this compound. 5. A modified figure of approximately 38000 is suggested for the molecular weight of the enzyme which contains one active site. [ABSTRACT FROM AUTHOR]

The amino acid sequences of two rat C-peptides corresponding to two rat proinsulins have been elucidated. Both C-peptides have 31 amino acids. There are differences in two positions, namely, in position 8 where rat-I has a proline and rat-II an alanine residue, and in position 17 where rat-I has a glutamic acid, rat-II a glycine residue. The additional acidic residue in rat-I C-peptide is counteracted by the additional basic residue in the insulin moiety of rat-I proinsulin (lysine B 29), which provides the two proinsulins with the same net charge at neutral pH. The amino acid sequences are: Glu-Val-Glu-Asp-Pro-Gln-Val-I:Pro/II:Ala -Gln-Leu-Glu-Leu-Gly-Gly-Gly-Pro-I: Glu:/II: Gly-Ala-Asp-Gly- Leu-Gln-Thr-Leu-Ala-Leu-Glu-Val-Ala-Arg-Gln. The rat C-peptides contain threonine and arginine, neither of which is present in the C-peptides of man, pig and ox. A comparison of the 5 sequences shows only 10 identical positions out of 31. [ABSTRACT FROM AUTHOR]

Both holo- and apo-aspartate-aminotransferase are sensitive to tetranitromethane; however, the inactivation which follows nitration is partial for the holoenzyme, and complete for the apoenzyme. Cysteinyl and tyrosyl residues are modified in both forms of the enzyme; in the apoenzyme a greater number of tyrosines are available to the reagent. The complete inactivation of the apoenzyme is correlated with the loss of only one tyrosyl residue, which is selectively modified under particular conditions. The loss of activity is caused by tile failure of the nitrated apoenzyme to recombine with the coenzyme. [ABSTRACT FROM AUTHOR]

The binding of fluorescein to bovine serum albumin was studied by equilibrium dialysis under various conditions At pH 8.0 and 5°C there are three binding sites with association constants of 2.8 x 104 M-1. Specific labeling of the binding sites using fluorescein-isothiocyanate showed that two of the binding sites are immediately adjacent. The labeled peptides were isolated and the sequence around one of the binding regions was determined revealing the presence of three lysines in this eight amino acid sequence. The binding is mainly caused by hydrophobic interactions and to lesser extent by electrostatic forces. The electrostatic contribution is much less than expected compared with other substances which are bound to bovine serum albumin. This is probably related to the fact that fluorescein is a nonphysiological compound and is "nonspecifically" bound to bovine serum albumin, Studies on binding properties of various peptic fragments of bovine serum albumin were performed. They showed that even slight fragmentation caused a drastic decrease in the ability to bind fluorescein. [ABSTRACT FROM AUTHOR]

The lysine sensitive aspartokinase of Escherichia coli has been obtained in a homogenous state from extracts of the strain Hfr H. the molecular weight of the protein has been determined by sedimentation equilibrium to be 130 000 daltons. The amino acid composition is given. [ABSTRACT FROM AUTHOR]

Absorption spectroscopy and circular dichroism measurements have been used to elucidate thc mechanism of lysozyme inactivation on photo-oxidation of the methionyl residues to methionine sulphoxide. The monosulphoxide derivative, which is formed by irradiation of the protein in aqueous solution, displayed spectral properties very similar to those of native lysozyme and retained about 54% enzyme activity. This reduced catalytic efficiency appeared to be due to limited conformational changes of the protein molecule. Striking differences were found, on the contrary, between the optical parameters of native lysozyme and of the di-sulphoxide derivative, which is prepared by irradiation in acetic acid solution and is almost devoid of enzyme activity. Studies on the unirradiated lysozyme demonstrated that this extensive denaturation was caused by the action of the protic solvent used. Whereas the acid-induced denaturation was reversible in the case of unmodified lysozyme, the photo-oxidation of the two methionyl residues irreversibly blocked the molecule in a largely disordered form. These results are discussed with respect to the location of the two methionines in the known atomic model of lysozyme. [ABSTRACT FROM AUTHOR]

We have studied the denaturation difference spectra of glyceraldehyde-3-phosphate dehydrogenase and lactic dehydrogenase in the 270–300mμ and 220–250mμ wavelength regions. When hydrogen ion concentration is varied in the range from pH 7 to pH 2, the absorption changes at 230–232 mμ are very similar to those at 291–293mμ with both dehydrogenases. The pH dependence of the optical rotatory parameters bo and [m′]232 follows a very similar pattern. The addition of sodium dodecyl sulfate induces hardly any change in the optical rotatory properties of the two dehydrogenases, while the difference spectra both in the near and in the far ultraviolet region closely resemble the corresponding denaturation difference spectra. The solvent perturbation spectra of aromatic chromophores due to 20% ethylene glycol exhibit a maximum in the far ultraviolet region at about 227mμ. At this wavelength, the extent of perturbation of tryptophan is 6.3 times greater than that of tyrosine. Calculations based on the far ultraviolet perturbation of aromatic chromophores suggest that the far ultraviolet denaturation difference spectra of the two dehydrogenases may be attributed to changes in the environment of aromatic chromophores, particularly of tryptophan. [ABSTRACT FROM AUTHOR]

Aggregates of two and more tRNASer molecules are formed from purified tRNAyeastSer under commonly used storage conditions. The aggregates can also be produced easily by adjusting to pH 3.0 a solution of tRNASer, Ser-tRNASer, or unfractionated tRNA and subsequently adding a neutral Mg++-containing buffer. The various aggregates were characterized by Sephadex elution profiles and by the rates of dissociation at elevated temperatures. At a given temperature, EDTA and phenol increase the rate of dissociation. The tRNASer aggregates were found to accept serine under the conditions of the enzymatic charging of the tRNASer monomer. The rate of charging is lower and the level of charging is only 1/3 to 1/2 of the one, which can be reached with the same aggregate sample after dissociation prior to the assay. Since the control experiments with the aim to explain the serine incorporation as an artefact (enzyme bound radioactivity; aggregate charging via charging of monomeric tRNA) were negative, the idea of a direct charging of the aggregates was accepted. [ABSTRACT FROM AUTHOR]

A fractionation procedure for avian erythrocyte histones was devised to give the six known, reproducible histone fractions from a single nuclear preparation, with limited manipulation and little wastage. The proposed method includes selective, two-step acid extraction, followed by cation-exchange chromatography and exclusion chromatography. The fractions were identified by amino acid analysis and by starch gel electrophoresis. The method is flexible in scale and permits a continuous balance of compositions and activities in metabolic experiments. Factors contributing to the relative extractability of histones from chromatin in acid were considered. The essential role of this step was the separation of erythrocyte-specific, serine-rich histone V, and arginine-rich histones III, IV, which otherwise would be eluted together from Amberlite CG-50 by guanidinium chloride. Two other arginine-rich components, more easily eluted in chromatograms of other tissues, were absent from the usual extracts of mature erythrocytes. However, similar components were produced from histones III, IV by treatment with β-mercaptoethanol. The conditions for good resolution of sub-fractions of moderately lysine-rich histones and of arginine-rich histones by exclusion chromatography on Bio-Gel P-60 and P-30 were examined. Reversible adsorption appeared to be more significant than pore size of the gel; the sulphates of arginine-rich histones were resolved better than the chlorides. [ABSTRACT FROM AUTHOR]

The histones of group F2(b) have been fractionated by acetone precipitation and by column chromatography on carboxymethylcellulose at pH 9. The acetone precipitation method enables F2(b), prepared on a large scale by extraction methods, to be further purified in bulk, the resulting product having 84% N-terminal proline. The column chromatography on carboxymethylcellulose at pH 9 has given 5 main fractions, two of which contain over 25% acidic amino acids (or their amides) and over 24% basic amino acids. [ABSTRACT FROM AUTHOR]

Earlier studies had shown that the enzyme tryptophan pyrrolase which catalyzes the first irreversible step in the conversion of tryptophan to functional nicotinyl derivatives in rat liver, was strongly inhibited by NADPH which may be considered the ultimate distal product in the conversion of tryptophan to derivatives of nicotinamide. As an extension of this work the present study has demonstrated that the administration of nicotinamide in vivo to adrenalectomized animals resulted in a strong suppression of the tryptophan-mediated elevation of tryptophan pyrrolase but had little or no effect on the hormonal induction of this enzyme by corticosteroids. These effects of nicotinamide were in sofar specific as analogs of this compound had little or no effect on the specific tryptophan-mediated elevation of tryptophan pyrrolase. Furthermore, the effect of nicotinamide was shown to be specific for the enzyme, tryptophan pyrrolase, having no effect on the tryptophan-mediated increase in serine dehydratase. By means of anti-tryptophan pyrrolase antibodies prepared in rabbits, the pulse labeling of tryptophan pyrrolasc in vivo by [14C]phenylalanine showed that, in animals pre-fed a 0% protein diet, tryptophan administration resulted in a doubling of the [14C]phenylalanine incorporation into tryptophan pyrrolase. Nico-tinamide administration completely abolished this effect of tryptophan but had little effect on the dramatic stimulation of tryptophan pyrrolase synthesis by hydrocortisone. It is postulated that nicotinamide may exert its inhibitory effect on tryptophan induced synthesis of tryptophan pyrrolase at the level of genetic translation. [ABSTRACT FROM AUTHOR]

Wheat seeds were imbibed and re-dried under conditions that did not give rise to radicle protrusion through the seed coat. When seeds pre-treated in this way were planted in moist vermiculite, coleoptile emergence was faster than from untreated seeds. This advancing effect on coleoptile emergence ('seed invigoration') was most marked when the seedlings were grown at low temperature or under osmotic stress (i.e. under unfavourable conditions). The seed-borne pathogen Septoria nodorum was not affected by an imbibing-drying treatment. Conditions of imbibition and drying giving optimal invigoration are described and data on the metabolism of untreated and invigorated seeds are presented. Oxygen uptake and [14C]- leucine incorporation into protein were more enhanced in aleurone layers than in embryos isolated from invigorated seeds. Both untreated and invigorated seeds showed very low α-amylase levels when dry, although α-amylase activity developed more rapidly in invigorated seeds during germination. Gibberellic acid alone was not able to replace an imbibing-drying treatment. [ABSTRACT FROM AUTHOR]

The amino acid and protein metabolism of roots of maize has been studied. The important role of the free amino acids and proteins of the roots as active agents in nitrogen assimilation is pointed out. Nitrogen supplied as nitrate is preferably incorporated into α-ketoglutaric acid, and then by transaminases transferred to other ketoacids. In the case of ammonia supply the function of a nitrogen-accumulating assimilation system leading to the formation of Arg, Glu-NH2 and Asp-NH2 is shown.

Canada thistle and field bindweed produce two metabolic derivatives from amitrole. These compounds, referred to as unknowns I and II, appear to be the same for both species. Conditions which favor an increase in the free-reducing sugar content of the leaves to which amitrole is applied appear to favor the production of unknown I. Under these conditions the formation of unknown II may not be favored. Unknown II does not appear to have phytocidal activity. A scheme for the biosynthesis of unknowns I and II and the equilibria between these compounds and amitrole is postulated. It is also postulated that amitrole must undergo a chemical reaction, possibly to unknown I, in order for translocation to occur. [ABSTRACT FROM AUTHOR]

The constitutive synthesis of β-galactosidase by a mutant strain of E. coli was studied under varied nutritional conditions. The advantage of expressing the experimental data in a way that permits comparisons of the differential rate of enzyme synthesis is stressed by the observation that compounds may have widely different effects on the rate of growth and on the rate of β-galactosidase formation. The exceptionally high rate of enzyme synthesis by cells grown on succinate is inhibited by lactate, lactose, glucose and galactose. Other compounds such as maltose, glycerol and amino acids also cause a marked but only temporary inhibition of the β-galactosidase synthesis, when they are added to succinate cultures. The observed effects on the rate of enzyme formation are discussed in relation lo the present knowledge of the mechanism of regulation of enzyme synthesis. The exceptionally strong inhibitory effect of lactose is assumed to be due to a feedback mechanism in which one or several products of the metabolism rather than lactose itself act as repressors of the enzyme formation. [ABSTRACT FROM AUTHOR]

1. The herbicide, 3-amino-1,2,4-triazole inhibits the growth of certain plant tissues grown in vitro; namely, Rumex, crown gall, habituated, and callus tissues. 2. Although the nature of the mechanism of the growth inhibition of these tissues by 3-AT was not investigated, three possible explanations seem worthy of further investigation; namely, a) possible interference of the biosynthesis of riboflavin b) possible interference with enzymatic systems containing phosporylase and hexokinase c) chelation effect of certain metals required in enzymatic processes. 3. 3-Amino 1,2,4-triazole should be studied for anticancer activity by virtue of its ability to prevent certain N to N or N to C linkages important to purines and their derivatives. [ABSTRACT FROM AUTHOR]

1. The enolase activity of cell-free extracts of Escherichia coli varies considerably with the conditions of growth. It is minute in cells grown on amino acids or succinate as the source of carbon but high in cells grown on high concentrations of carbohydrates or glycerol. 2. The anaerobic growth of the organism is inhibited by low concentrations of fluoride in a synthetic mineral salts medium with glucose as the sole source of carbon. Similar or higher concentrations of fluoride have no or very slight effect on aerobic growth. Anaerobic growth in the presence of a suitable hydrogen acceptor such as an amino acid or nitrate, is also insensitive to fluoride. 3. The possible significance of these results is discussed in relation to the well-known effect of fluoride on the glycolytic pathway of metabolism. The variations in the enolase activity are considered to indicate that this pathway is indispensable or made extensive use of only under limited conditions of growth. [ABSTRACT FROM AUTHOR]

1. 3-Amino-1,2,4-triazole (ATA) was found to have very little effect upon the metabolism by bean plants of NaHC14O3, succinate-2,3-C14, and glucose-U-C14. 2. The effect of ATA upon the metabolism of glycine-1-C14, glycine-2-C14, glycine-U-C14, and serine-U-C14 was quite striking. In the presence of a high percentage of radioactivity from these labeled compounds entered an unidentified compound previously reported to be a metabolic product of ATA. 3. The unidentified compound, compound "1", does not appear to be an iron chelate or a sugar adduct. It may possibly be 3-amino-1,2,4-triazolylalanine but this, too, appears unlikely. 4. It is postulated that the phytotoxicity of ATA may result in part from interference in the normal metabolism of glycine and serine. [ABSTRACT FROM AUTHOR]

1. Pure cultures of Scenedesmus obliquus were grown with aspartic acid, succinamide and asparagine as a source of nitrogen, and growth, nitrogen assimilation and ammonia production were determined every three days. 2. In the aspartic acid cultures cell division took place at a low but constant rate for three months. The N-assimilation was also low but constant. The nitrogen content of the individual cell amounted to approximately 6·10-10 mg. Ammonia could not be demonstrated in the culture medium. 3. With succinamide the same final cell count was attained as with aspartic acid, viz. 6,000 per mm3, but growth was already completed after eighteen days. The N-assimilation ceased at the same time as the cell division, and the N-content of the individual cell was the same as in the preceding case. Ammonia was present in the nutrient solution throughout the entire experiment. 4. The rate of growth with asparagine was intermediate between the two foregoing. An inhibition in growth took place first after fifty days and therefore the final cell count was higher than in the two preceding experiments, 10,000 per mm3. The N-assimilation proceeded similarly to about the fiftieth day, when the N-content of the cells amounted to 30·10-10 mg per cell. 5. In agreement with the idea that amido-N and amino-N are split off according to different mechanisms the rates of the N-utilization show great differences. With succinamide it is thus sixteen times greater than with aspartic acid. Asparagine resembles succinamide most closely, which indicates that the amido-N is the first to be utilized. This had been confirmed by chemical analyses. 6. The experimental results have been discussed and the sources of nitrogen compared with one another. Comparisons have also been made with earlier studied amino acids, glycocoll and alanine. 7. The fact that aspartic acid is the poorest of the nitrogen sources has been discussed and the hypothesis set up that the key position in the nitrogen metabolism of Seenedesmus obliquus is not occupied by aspartic acid but by glulamic acid, similar to what is the case in many higher plants. [ABSTRACT FROM AUTHOR]

A new group of chromatin-associated proteins having a high content of acidic and basic amino acids have been isolated from the 0.35M NaCl-extractable proteins from calf thymus. This new group, designated ‘high-mobility group’ proteins have been partially separated and some interesting new proteins identified. One such protein contains over 55% acidic and basic amino acids. [ABSTRACT FROM AUTHOR]

The reaction of L-phenylalanine, a stereospecific and uncompetitive inhibitor, with human placental alkaline phosphatase in the free and phosphoryl forms was investigated, using a rapid mixing and quenching technique. It is established that, at pH 8—9, L-phenylalanine reacts instantaneously with phosphoryl phosphatase preventing dephosphorylation at concentrations similar to those causing inhibition in the steady state. It is further established that at pH 9 · L-phenylalanine produces an increase in the steady state concentration of phosphoryl phosphatase, amounting to over 80% of the total enzyme with 5 mM L-phenylalanine. At high inhibitor concentration the same steady-state activity was observed with a variety of phosphate ester substrates that different widely in affinity and reactivity. All these results are consistent with a mechanism whereby L-phenylalanine prevents dephosphorylation while other schemes giving rise to uncompetitive inhibition are excluded. It is suggested that only the basic form of L-phenylalanine is inhibitory and possible mechanisms are discussed. [ABSTRACT FROM AUTHOR]