Arginine in the salt-induced peptide formation reaction: enantioselectivity facilitated by glycine, l- and d-histidine

The salt-induced peptide formation reaction has been proposed as a conceivable preliminary to the prebiotic evolution of peptides. In the present paper, the behaviour of arginine is reported for this reaction together with a discussion of the catalytic effects of glycine, and l- and d-histidine. Importantly, the behaviour of the two histidine enantiomers is different. Both histidine enantiomers perform better than glycine in enhancing the yields of arginine dipeptide with l-histidine being more effective than d-histidine. Yields in the presence of histidine are up to 70 times greater than for arginine solutions alone. This compares with 4.2 times higher in the presence of glycine. This difference is most pronounced in the most concentrated (containing 80 mM arginine) reaction solution where arginine has the lowest reactivity. A distinct preference for dimerisation of l-arginine also appears in the 80 mM cases for catalyses of other amino acids. This phenomenon is different from the behaviour of aliphatic amino acids, which display obvious inherent enantioselectivity for the l-stereomers in the SIPF reaction on their own rather than when catalysed by glycine or histidine.     

Cyanide formation in preparations from Chlorella and New Zealand spinach leaves: Effect of added amino acids

Summary As part of an effort to identify the natural precursor(s) of HCN in the alga Chlorella vulgaris Beijerinck, and in leaves of New Zealand spinach (Tetragonia expansa, Murr.), HCN release was measured after addition of various amino acids to illuminated algal extracts and grana preparations. Histidine is particularly effective as an HCN precursor, both with Chlorella extracts and leaf grana. With the algal extracts, d-histidine is about ten times more effective than l-histidine and histamine, whereas the two isomers (and histamine) are about equally effective with leaf grana. In the presence of leaf grana plus added Mn²⁺ and peroxidase, l-tyrosine and l-cysteine like-wise cause HCN formation; but these amino acids cause little or no HCN formation in the presence of Chlorella extracts. A stimulation of HCN production by l-histidine was observed with intact Chlorella cells. Because of the limitations of the assay method, the possibility can not be excluded that other substances than histidine may also lead to HCN generation in Chlorella vulgaris, but the results show that histidine has an important role in HCN generation by this species.Abbreviation POD peroxidase     

Partial Purification and Some Properties of 7-Keto-8-aminopelargonic Acid Synthetase,an Enzyme Involved in Biotin Biosynthesis

7-Keto-8-aminopelargonic acid synthetase (KAPA synthetase) which catalyzes the formation of KAPA from pimelyl CoA and l-alanine, and is involved in biotin biosynthesis, was partially purified from a cell-free extract of Bacillus sphaericus by a procedure involving ammonium sulfate fraction ation, protamine treatment, and DEAE-cellulose column chromatography. The reaction product was bioautographically confirmed to be KAPA. Some properties of the enzyme were also investigated. Among the amino acids, only l-alanine was active as a substrate, condensing with pimelyl CoA, The reaction required pyridoxal phosphate but the other vitamin B₆ compounds were inert. Typical inhibitors of pyridoxal phosphate enzymes showed marked inhibition to the reaction. Various amino acids such as l-cysteine, glycine, d-alanine, l-serine, l-histidine, and d-histidine were also found to be inhibitory.     

Catalytic effects of glycine on prebiotic divaline and diproline formation

The catalytic effects of the simple amino acid glycine on the formation of diproline and divaline in the prebiotically relevant salt-induced peptide formation (SIPF) reaction was investigated in systems of different amino acid starting concentrations and using the two enantiomeric forms of the respective amino acid. Results show an improved applicability of the SIPF reaction to prebiotic conditions, especially at low amino acid concentrations, as presumably present in a primordial scenario, and indicate excellent conditions and resources for chemical evolution of peptides and proteins on the early earth. For valine, furthermore differences in catalytic yield increase are found indicating a chiral selectivity of the active copper complex of the reaction and showing a connection to previously found enantiomeric differences in complex formation constants with amino acids.     

Losses and biogeochemical cycling of soil organic nitrogen with prolonged arable cropping in the South African Highveld – evidence from - and -amino acids

We know little about the mechanisms that cause rapid losses in the soil organic N pool during cropping. As the analysis of amino acid enantiomers can provide insight into both the fate of microbial N and the ageing of cells in the environment, we used this technique as a tool to examine how the pool of protein-bound N in subtropical Plinthosols responds to increasing duration of arable cropping. The samples comprised bulk soils (0–20 cm) and clay fractions from each of three agro-ecosystems in semiarid South Africa; the sites have been cropped for periods varying from 0 to 98 years. The amino acid enantiomers contributed 34% to the total N content. With increasing number of years a piece of land has been cropped, the amino acid concentrations declined bi-exponentially to about 30% of their initial level in the native grasslands. Changes of the remaining soil protein-N pool were indicated by alterations in the d-content of individual amino acids. As the years of arable cropping increased, the proportions of d-alanine and d-glutamic acid increased relative to the respective l-enantiomers. This was attributed to an accumulation of N in residues of bacterial cell walls. In contrast, the d/l-ratios of leucine and aspartic acid declined in the long-term cultivated plots, probably reflecting losses of old amino acid-N reserves at the most degraded arable land.     

Transport ofl-histidine by human diploid fibroblasts in culture

Summary The transport ofl-histidine has been characterized in skin derived diploid human fibroblasts, cultured under strictly controlled conditions. The transport measurements were made on cells grown to subconfluency after 60 to 90 min timed preincubation. The data, at substrate concentrations ranging from 0.050 to 10 mmol/l, were analyzed by a computer program. A saturable transport system (K _m =0.25 mmol/l, V _max =17 nmol/mg protein per min) and a nonsaturable component of influx (K _d =1.6±0.4 nmol/mg protein/min per mmol) were found.l-Histidine displayed no Na⁺ requirement at either low or high concentrations. Inhibition analysis demonstrated thatl-histidine uptake at low concentration was poorly inhibited by amino acids known to be effective inhibitors of system A. The largest fraction ofl-histidine uptake was inhibited by 2-amino-bicyclo (2,2,1)-heptane-2-carboxylic acid (BCH), leucine, and tryptophan. These results indicated thatl-histidine is transported in human fibroblasts, mainly by the Na⁺ independent system L. The differences between this cell type and others studied previously are discussed. This work was supported in part by Grant 773 from UER de Médecine, Université Paris XI (France).     

Depression of by-product formation during l-isoleucine production by a living-cell reaction process

Summary Two unnatural and unwanted amino acids, norvaline (Nva) and O-ethylhomoserine (O-EH) are formed as by-products in l-isoleucine production by Brevibacterium flavum AB-07 using a new process named the living cell reaction process. Nva formation was depressed by using a leucine auxotrophic mutant (AB-07-Leu-2) derived from strain AB-07. It was found that Nva formation was closely related to leucine biosynthesis. O-EH formation was repressed by addition of l-methionine to the reaction mixture. However, the homoserine-O-acetyltransferase of AB-07-Leu-2 was not subject to either inhibition or repression by addition of l-methionine. Furthermore, the O-EH-forming enzyme, which converts O-acetylhomoserine to O-EH, was speculated to be repressed by l-methionine. Offprint requests to: H. Yukawa     

Mechanism of the suppression against <Emphasis Type="SmallCaps">d</Emphasis>-galactosamine-induced hepatic injury by dietary amino acids in rats

To elucidate the mechanism by which dietary amino acids suppress the d-galactosamine (d-GalN)-induced hepatitis, we examined the involvement of Kupffer cells, tumor necrosis factor-α (TNF-α) and apoptosis in the mechanism. In experiment 1, the rats were fed with 10%l-glutamine or 5% glycine diet injected with d-GalN with or without gadolinium chloride (GdCl₃)-pretreatment. The results indicated that these amino acids suppressed the d-GalN-induced elevation of serum transaminase activities, irrespective of GdCl₃-pretreatment. In experiment 2, rats were fed with 10% of l-glutamine, l-serine, l-alanine or l-glutamic acid diets injected with d-GalN. The results demonstrated that all these amino acids suppressed the d-GalN-induced elevation of serum transaminase activities, but that serum TNF-α concentrations and hepatic caspase-3 activities in the rats were not appreciably changed. In conclusion, the suppressive effects of amino acids on d-GalN-induced hepatitis were suggested not to be always mediated by the inhibition of Kupffer cells → TNF-α → apoptosis pathway.     

Regulation of the formation of protease inBacillus megaterium

Protease is synthesized by the cultures growing in a glucose-containing mineral medium. However, it is formed even during incubation of the washed cells in a nitrogen free medium. The enzyme synthesis is decreased substantially by the addition of the individual amino acids or their mixture. Threonine, isoleucine, leucine and valine are the most inhibitory. Arginine, cysteine, glycine, lysine and tryptophan in concentrations of 10³ m do not inhibit the production of protease. The growth of the culture is also somewhat inhibited by threonine and isoleucine, the repression of protease being, however, much higher. Concentrations of 10³ m inhibit its synthesis by 80–90%. However, the enzyme activity is not influenced. The inhibition is caused byl,-isomers. Repression of the enzyme synthesis after the addition of threonine into the medium is much greater in a growing culture than in a culture starving in a nitrogen-free medium. However the level of free threonine in the pool is roughly the same in both growing and non-growing cultures. A mixture of 13 amino acids, which themselves are little inhibitory, suppresses the synthesis of protease much more than threonine or isoleucine. The inhibitory effect of the individual amino acids on the enzyme formation is apparently additive.     

Effect of amino acids on growth ofSphaerotilus discophorus

The effect of casein hydrolysate, of mixtures of amino acids and of individual amino acids on the growth of 4 strains ofSphaerotilus discophorus was determined. Growth was virtually completely inhibited by 1.0% Bacto Casamino Acids, 0.54% simulated casein hydrolysate and 0.2% of a uniform mixture of 18 amino acids. The latter were prepared withl amino acids except thatdl-serine,dl-valine anddl-threonine were present in the uniform amino acid mixture.Experiments designed to test the toxicity of the 18 individual amino acids at 0.018 – 0.36% concentration indicated that arginine, glutamic acid, leucine, lysine and proline were non-toxic. However, aspartic acid and methionine were moderately toxic; growth was greatly repressed at a concentration of 0.36%. The remaining 11 amino acids which included alanine, cystine, glycine, tyrosine, histidine, isoleucine, phenylalanine, serine, threonine, tryptophane and valine were the most toxic of the group. They prevented growth partially or completely, at a concentration of 0.18% or 0.36%.dl-Serine anddl-valine were especially toxic and prevented growth at a concentration of 0.018%. The toxicity of the individuall-amino acids can account for the toxicity of Casamino Acids and simulated casein hydrolysate. l-Methionine or cyanocobalamin (vitamin B₁₂) is required for the growth ofS. discophorus. Alsod- anddl-methionine can replace cyanocobalamin although they completely repress growth when used at the relatively high concentration of 200 µg per ml of medium.     

Preparation and reactivity studies of synthetic microperoxidases containing<Emphasis Type="Italic"> b</Emphasis>-type heme

In order to create a heme environment that permits biomimicry of heme-containing peroxidases, a number of new hemin–peptide complexes—hemin-2(18)-glycyl-l-histidine methyl ester (HGH), hemin-2(18)-glycyl-glycyl-l-histidine methyl ester (HGGH), and hemin-2,18-bis(glycyl-glycyl-l-histidine methyl ester) (H2GGH)—have been prepared by condensation of glycyl-l-histidine methyl ester or glycyl-glycyl-l-histidine methyl ester with the propionic side chains of hemin. Characterization by means of UV/vis- and ¹H NMR spectroscopy as well as cyclic- and differential pulse voltammetry indicates the formation of five-coordinate complexes in the case of HGH and HGGH, with histidine as an axial ligand. In the case of H2GGH, a six-coordinate complex with both imidazoles coordinated to the iron center appears to be formed. However, ¹H NMR of H2GGH reveals the existence of an equilibrium between low-spin six-coordinate and high-spin five-coordinate species in solution. The catalytic activity of the hemin–peptide complexes towards several organic substrates, such as p-cresol, l-tyrosine methyl ester, and ABTS, has been investigated. It was found that not only the five-coordinate HGH and HGGH complexes, but also the six-coordinate H2GGH, catalyze the oxidation of substrates by H₂O₂. The longer and less strained peptide arm provides the HGGH complex with a slightly higher catalytic efficiency, as compared with HGH, due to formation of more stable intermediate complexes.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00775-004-0532-5.Abbreviations ABTS 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) - DCC dicyclohexylcarbodiimide - HGH hemin-2(18)-glycyl-l-histidine methyl ester - HGGH hemin-2(18)-glycyl-glycyl-l-histidine methyl ester - H2GGH hemin-2,18-bis(glycyl-glycyl-l-histidine methyl ester) - HOBt N-hydroxybenzotriazole     

Utilization ofd-amino acids byFusobacterium nucleatum andFusobacterium varium

Summary The utilization ofd- andl -amino acids with acidic, basic or polar side chains was demonstrated by HPLC. Two species of the anaerobeFusobacterium utilized D-lysine and the L isomers of glutamate, glutamine, histidine, lysine and serine. OnlyF. varium usedl-arginine,d-glutamate andd-serine as substrates, whereasF. nucleatum specifically utilizedd-histidine andd-glutamine.d-Glutamate accumulated in F. nucleatum cultures supplemented withd-glutamine, and ornithine was detected when eitherdl- orl-arginine was included inF. varium cultures. Based on literature precedents,d-glutamate andd-histidine are isomerized to their L isomers prior to degradation, but separate catabolic pathways are possible for each enantiomer of lysine and serine.     

Comparative immunological properties of enantiomeric peptides

Summary The immunogenicity of a peptide composed of only d-amino acids is compared with that of the corresponding l-peptide enantiomer. Following three administrations of 100 g of individual peptide formulated with different adjuvants (Freund's complete adjuvant, QS21, or alum) to BALB/c mice, guinea pigs and rabbits, the l-peptide elicited strong l-peptide-specific IgG antibody responses in all formulations, whereas the d-peptide-induced d-peptide-specific IgG antibodies in the Freund's complete adjuvant and QS21 formulations, but was nonimmunogenic in the alum formulation. Mouse T-cell lines induced by the d-peptide formulated in Freund's complete adjuvant were found to express significant amounts of IL-2 when they were stimulated by the d-peptide. When an equal amount of both enantiomers was mixed and administered in Freund's complete adjuvant, only an l-peptide-specific IgG antibody response was observed. These results suggest that (i) d-peptide is immunogenic when strong adjuvant is provided; (ii) the immune system has preferential recognition of l-amino acid peptide; and (iii) the d-peptide can elicit d-peptide-specific T-cell responses.     

d-Aspartyl residue in a peptide can be liberated and metabolized by pig kidney enzymes

Summary The presence of an enzyme activity which hydrolyzes glycyl-d-aspartate was found in the homogenates of pig kidney cortex. The activity was inhibited by metal chelating agents and cilastatin, suggesting that the enzyme was a cilastatin-sensitive metallo-peptidase. Of the two hydrolysis products,d-aspartate was found to be less accumulated than glycine. The fate ofd-aspartate was, therefore, examined and the amino acid was found to be converted tol-aspartate,l-alanine and pyruvate, in the presence ofl-glutamate. Experiments with enzyme inhibitors suggested that the conversion involvedd-aspartate oxidase, aspartate aminotransferase and alanine aminotransferase as well as decarboxylation of oxaloacetate produced fromd-aspartate. All the results indicate that the enzymes in the pig kidney can liberate thed-aspartyl residue in the peptide and convert it to the compounds readily utilizable. The finding suggests a probable metabolic pathway of thed-aspartate-containing peptide.     

Methionine peptide formation under primordial earth conditions

According to recent research on the origin of life it seems more and more likely that amino acids and peptides were among the first biomolecules formed on earth and that a peptide/protein world was thus a key starting point in evolution towards life. Salt-induced Peptide Formation (SIPF) has repeatedly been shown to be the most universal and plausible peptide-forming reaction currently known under prebiotic conditions and forms peptides from amino acids with the help of copper ions and sodium chloride. In this paper we present experimental results for salt-induced peptide formation from methionine. This is the first time that a sulphur-containing amino acid was investigated in this reaction. The possible catalytic effects of glycine and l-histidine in this reaction were also investigated and a possible distinction between the l- and d-forms of methionine was studied as well.     

Effect of 2-deoxy-d-Glucose on Aminoacids Metabolism in Rats’ Cerebral Cortex Slices

We studied the effect of different concentrations of 2-deoxy-d-glucose on the l-[U-¹⁴C]leucine, l-[1-¹⁴C]leucine and [1-¹⁴C]glycine metabolism in slices of cerebral cortex of 10-day-old rats. 2-deoxy-d-glucose since 0.5 mM concentration has inhibited significantly the protein synthesis from l-[U-¹⁴C]leucine and from [1-¹⁴C]glycine in relation to the medium containing only Krebs Ringer bicarbonate. Potassium 8.0 mM in incubation medium did not stimulate the protein synthesis compared to the medium containing 2.7 mM, and at 50 mM diminishes more than 2.5 times the protein synthesis compared to the other concentration. Only at the concentration of 5.0 mM, 2-deoxy-d-glucose inhibited the CO₂ production and lipid synthesis from l-[U-¹⁴C] leucine. This compound did not inhibit either CO₂ production, or lipid synthesis from [1-¹⁴C]glycine. Lactate at 10 mM and glucose 5.0 mM did not revert the inhibitory effect of 2-deoxy-d-glucose on the protein synthesis from l-[U-¹⁴C]leucine. 2-deoxy-d-glucose at 2.0 mM did not show any effect either on CO₂ production, or on lipid synthesis from l-[U-¹⁴C]lactate 10 mM and glucose 5.0 mM.     

Preferential amino acid sequences in alumina-catalyzed peptide bond formation

The catalytic effect of activated alumina on amino acid condensation was investigated. The readiness of amino acids to form peptide sequences was estimated on the basis of the yield of dipeptides and was found to decrease in the order glycine (Gly), alanine (Ala), leucine (Leu), valine (Val), proline (Pro). For example, approximately 15% Gly was converted to the dipeptide (Gly(2)), 5% to cyclic anhydride (cyc(Gly(2))) and small amounts of tri- (Gly(3)) and tetrapeptide (Gly(4)) were formed after 28 days. On the other hand, only trace amounts of Pro(2) were formed from proline under the same conditions. Preferential formation of certain sequences was observed in the mixed reaction systems containing two amino acids. For example, almost ten times more Gly-Val than Val-Gly was formed in the Gly+Val reaction system. The preferred sequences can be explained on the basis of an inductive effect that side groups have on the nucleophilicity and electrophilicity, respectively, of the amino and carboxyl groups. A comparison with published data of amino acid reactions in other reaction systems revealed that the main trends of preferential sequence formation were the same as those described for the salt-induced peptide formation (SIPF) reaction. The results of this work and other previously published papers show that alumina and related mineral surfaces might have played a crucial role in the prebiotic formation of the first peptides on the primitive earth.     

Removal of <Emphasis Type="SmallCaps">l</Emphasis>-alanine from the production of <Emphasis Type="SmallCaps">l</Emphasis>-2-aminobutyric acid by introduction of alanine racemase and <Emphasis Type="SmallCaps">d</Emphasis>-amino acid oxidase

l-2-Aminobutyric acid can be synthesized in a transamination reaction from l-threonine and l-aspartic acid as substrates by the action of threonine deaminase and aromatic aminotransferase, but the by-product l-alanine was produced simultaneously. A small amount of l-alanine increased the complexity of the l-2-aminobutyric acid recovery process because of their extreme similarity in physical and chemical properties. Acetolactate synthase has been introduced to remove the pyruvate intermediate for reducing the l-alanine concentration partially. To eliminate the remnant l-alanine, alanine racemase of Bacillus subtilis in combination with d-amino acid oxidase of Rhodotorula gracilis or Trigonopsis variabilis respectively was introduced into the reaction system for the l-2-aminobutyric acid synthesis. l-Alanine could be completely removed by the action of alanine racemase of B. subtilis and d-amino acid oxidase of R. gracilis; thereby, high-purity l-2-aminobutyric acid was achieved. The results revealed that alanine racemase could discriminate effectively between l-alanine and l-2-aminobutyric acid, and selectively catalyzed l-alanine to d-alanine reversibly. d-Amino acid oxidase then catalyzed d-alanine to pyruvate stereoselectively. Furthermore, this method was also successfully used to remove the by-product l-alanine in the production of other neutral amino acids such as l-tertiary leucine and l-valine, suggesting that multienzymatic whole-cell catalysis can be employed to provide high purity products.     

Uptake of amino acids by actidione-treated yeast cells

Uptake of glyeine,l-cysteine,l-leucine,l-methionine,l-aspartic acid andl-lysine was investigated in resting cells ofSaccharomyces cerevisiae treated with 0.3mm actidione for blocking protein synthesis. The amino acids were taken up against substantial concentration gradients (up to nearly 1,000∶1 for μm l-cysteine and glycine). They were present in the free form inside the cells. Their unidirectional transmembrane fluxes were under a negative feedback control by the intracellular concentration of the amino acid involved. The amino acids tested apparently employed more than one transport agéncies for their membrane passage, the half-saturation constants being 6.2–7.7×10⁻⁴ m for glycine, 2.5×10⁻⁴ m forl-cysteine, 6×10⁻⁵ and 4×10⁻⁴ m forl-lysine, 3×10⁻⁵ and 6×10⁻⁴ m forl-methionine, 7–18×10⁻⁵ and 1.6×10⁻³ m forl-aspartic acid and 6×10⁻⁵ and 2×10⁻³ m forl-leucine. The specificities of the transport systems are overlapping but there emerges a wide-affinity transport system for glycine, alanine, leucine, methionine, serine, cysteine, phenylalanine, aspartic acid, asparagine, glutamic acid and tryptophan (and possibly for other amino acids), and more specific systems for each of the following: glycine, lysine, methionine, histidine, arginine, and aspartic and glutamic acids. Proline had the peculiar effect of stimulating the transport of all the amino acids tested. The amino acids apparently interacted in the uptake not only by competition for the binding site but also by allotopic inhibition (e.g.l-cysteine) and possibly stimulation (l-proline). The initial rate of uptake of amino acids and their steady-state level of distribution were characterized by identical activation energies: 7.5 kcal/mole forl-lysine, 6.9 kcal/mole forl-aspartic acid, and 13.2 kcal/mole for glycine.     

Transport of glutamine inXenopus laevis oocytes: Relationship with transport of other amino acids

Summary We have investigated transport of the amino acid glutamine across the surface membranes of prophase-arrestedXenopus laevis oocytes. Glutamine accumulation was linear with time for 30 min; it was stereospecific with aK _m of 0.12±0.02mm andV _max of 0.92±0.17 pmol/oocyte · min forl-glutamine. Transport ofl-glutamine was Na⁺-dependent, the cation not being replaceable with Li⁺, K⁺, choline, tris(hydroxymethyl)-aminomethane (Tris), tetramethylammonium (TMA) or N-methyld-glucamine NMDG); external Cl^– appeared to be necessary for full activation of Na⁺-dependent glutamine transport. Two external Na⁺ may be required for the transport of one glutamine molecule.l-glutamine transport (at 50 m glutamine) was inhibited by the presence of other amino acids:l-alanine,d-alanine,l-leucine,l-asparagine andl-arginine (about 60% inhibition at 1mm);l-histidine,l-valine and glycine (25 to 40% inhibition at 1mm);l-serine,l-lysine,l-phenylalanine andl-glutamate (45 to 55% inhibition at 10mm). N-methylaminoisobutyric acid (meAIB) had no effect at 10mm, but 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) inhibited Na⁺/glutamine transport by about 50% at 10mm.l-glutamine was a competitive inhibitor of the Na⁺-dependent transport ofl-alanine,d-alanine andl-arginine; this evidence is consistent with the existence of a single system transporting all four amino acids. Glutamine uptake in oocytes appears to be catalyzed by a transport system distinct from the cotransport Systems A, ASC, N and Gly, although it resembles System B^0,+.