Studies on the Decarboxylation of Amino Acids with Glyoxal

Decarboxylation of about twenty kinds of α, β and γ-amino acids in the reaction with glyoxal or ninhydrin was investigated. The decarboxylation rate of amino acids proved that steric and polar effects had important roles in the reaction.

From the data of pK₂ values and decarboxylation rates of amino acids, it can be concluded that under a similar steric environment, the decarboxylation rate depends on the anion concentration of amino acids.

Besides carbon dioxide, acetaldehyde, 2-propanone and propionaldehyde were respectively detected from the reaction of β-alanine, β and γ-amino-n-butyric acids with glyoxal or ninhydrin. The decarboxylation mechanism of these amino acids seemed to take place through the corresponding β- or γ-keto acid.

Oxygen absorption was also observed from the reaction of amino acids with dicarbonyl compounds.     

Hydrolysis technology of biomass waste to produce amino acids in sub-critical water

Hydrolysis of biomass waste (such as fish waste, chicken waste, hair and feather) to produce amino acids was studied in sub-critical water, with reaction temperatures from 180 to 320 degrees C and reaction pressures from 3 to 30 MPa. The product of amino acid was determined by Amino Acid Analyzer (BioLC), and 18 kinds of amino acid were obtained. The results show that the controlling of reaction atmosphere, pressure, temperature and time of hydrolysis is very important to obtain high yield of amino acid; most of amino acids reached maximum yield at reaction temperature range of 200-290 degrees C and reaction time range of 5-20 min. There are obvious changes of amino acids yield at reaction pressures of 6-16 MPa and reaction temperature around 260 degrees C, owing to the homogeneousness of the first two phases of water in the formation of vapor and liquid. There are different yields of the same amino acid in different reaction atmospheres (e.g. air, carbon dioxide and nitrogen).     

Determination of isokinetic ratios necessary for equimolar incorporation of carboxylic acids in the solid-phase synthesis of mixture-based combinatorial libraries

The methods used to study the relative reaction rates of 45 different aliphatic and aromatic carboxylic acids when coupled to resin-bound amino acid amides is described. Competition experiments involving the coupling of incoming carboxylic acids to resin-bound amino acid amides were performed. The relative composition of each N-acylated amino acid amide in the resulting mixtures was compared to controls prepared by physically mixing equal aliquots of individual compounds in order to study the relative reaction rates of the incoming carboxylic acids. The ratios of the incoming carboxylic acids were then iteratively adjusted to yield as close to equimolar products as possible. As expected, the steric and electronic nature of the incoming carboxylic acids was found to influence their relative reaction rates. The steric hindrance of the resin-bound amino acid appears to have a proportional effect on the reaction rates of the incoming carboxylic acids. N-acylated amino acid amides in the final mixtures, prepared using the final isokinetic ratios, were found to be approximately equimolar.     

Sensitivity of the Rana temporaria tadpole chemoreceptor system to amino acids

In behavioural experiments, studies have been made of the sensitivity of frog tadpoles to amino acids and creatine. The best index of stimulus perception was found to be the alimentary reaction of tadpoles to presentation of the solved substances. For different amino acids, the intensity of the evoked reaction decreases in the following order: ornithine--valine--lysine--isoleucine--arginine--glutamine and tryptophan--cysteine--asparagine--alanine--beta-phenylalanine--glycine. The effectiveness of creatine is rather high, i. e. between tryptophan and cysteine. In tadpoles from two age groups, threshold concentrations of some amino acids were determined which evoke alimentary reaction. It was shown that the sensitivity to 4 amino acids (from 5 investigated ones) decreases with age, the sensitivity to valine remaining unaffected.     

Posttranslational Protein Modification by Amino Acid Addition in Intact and Regenerating Axons of the Rat Sciatic Nerve

Abstract: Experiments were performed to determine whether ppsttranslational addition of amino acids to axonal proteins occurs in axons of the rat sciatic nerve. Two ligatures were placed 1 cm apart on sciatic nerves. Six days later, segments proximal to each ligature were removed, homogenized, centrifuged at 150,000 · g , and analyzed for the ability to incorporate ³H-amino acids into proteins. No incorporation of amino acids into proteins was found in the high-speed supernatant, but when the supernatant was passed through a Sephacryl S-200 chromatography column (removing molecules less than 20 kD), [³H]arginine, lysine, leucine and aspartic acid were incorporated into proteins in both proximal and distal nerve segments. Small but consistently greater amounts of radioactivity were incorporated into proteins in proximal segments compared with distal segments, indicating that the components necessary for the reaction are transported axonally. This reaction represents the posttranslational incorporation of a variety of amino acids into proteins of rat sciatic nerve axons. Other experiments showed that the incorporation of amino acids into proteins is by covalent bonding, that the amino acid donor is likely to be tRNA, and that the reaction is inhibited in vivo by a substance whose molecular mass is less than 20 kD. This inhibition is not affected by incubation with physiological concentrations of unlabeled amino acids, by boiling, or by treatment with Proteinase K. When the axonally transported component of the reaction was determined in regenerating nerves, the amount of incorporation of amino acids into protein was 15–150 times that in intact nerves. The results indicate that the components of this reaction are transported axonally in rat sciatic nerves and that the reaction is increased dramatically in growing axons during nerve regeneration.     

Amino acid analysis with o-phthalaldehyde detection: effects of reaction temperature and thiol on fluorescence yields.

Chromatographic separation of amino acids with fluorometric detection of the o-phthalaldehyde-thiol reaction product offers an analytical system of high sensitivity for most amino acids. The fluorescence yield for amino acids having a fully substituted carbon atom in the α-position with respect to the amino group can be substantially improved by increasing the temperature of the reaction with o-phthalaldehyde-thiol and by substituting either ethanethiol or methanethiol for the more commonly used β-mercaptoethanol. The analytical sensitivity for these α-branched amino acids is thus brought into line with that for the other primary amino acids. A comparison of chromatograms obtained at reaction temperatures of 25 and 100°C allows recognition of amino acids of this type in complex mixtures by the substantial increase in fluorescence yield at 100°C.     

Pitfalls in using sodium hypochlorite as a seed disinfectant in C incorporation studies

Seeds sterilized with sodium hypochlorite (NaOCl) retained sufficient amounts to interfere with studies of amino acid metabolism of the sterilized seeds during germination. Repeated washing in water did not remove NaOCl completely. However, soaking the seeds for 10 min in 0.01 n HCl removed NaOCl completely, without reducing germinability.Residual NaOCl reacted with the amino acids and reduced their concentrations in the incubation media. This reaction resulted in high production of CO(2) and low uptake of amino acids by the seeds. Decarboxylation of the amino acids occurred in the incubation medium outside the seed, was independent of the presence of seeds in the reaction, and therefore was not related to amino acid metabolism by the seeds. Effects of NaOCl on uptake, incorporation, and CO(2) production from indoleacetic acid were similar to those of the amino acids studied.     

利用液相色谱研究烘焙条件对白肋烟中游离氨基酸的影响

利用OPA、FMOC联合在线衍生反相高效液相色谱法测定白肋烟在110℃、120℃、130℃、140℃、150℃分别烘焙12m in和16 m in后游离氨基酸的含量,研究烘焙温度和烘焙时间对白肋烟中游离氨基酸的影响。结果显示整个烘焙过程是蛋白质的降解和M ailard反应相结合的动态过程,蛋白质的降解主要发生在110℃~120℃的低温区;而M ailard反应主要发生在130℃~150℃高温区。实验结果还表明烘焙时间对白肋烟在烘焙后游离氨基酸的含量有重要影响,烘焙时间的延长使烟叶中的游离氨基酸均有较大幅度降低,其中影响最明显的是Pro、Asp和Asn。     

Hydrothermal production and characterization of protein and amino acids from silk waste

Non-catalytic hydrothermal decomposition of sericin and fibroin from silk waste into useful protein and amino acids was examined in a closed batch reactor at various temperatures, reaction times, and silk to water ratios to examine their effects on protein and amino acid yields. For the decomposition of sericin, the highest protein yield was found to be 0.466 mg protein/mg raw silk, obtained after 10 min hydrothermal reaction of silk waste at 1:100 silk to water ratio at 120 degrees C. The highest amino acid yield was found to be 0.203 mg amino acids/mg raw silk, obtained after 60 min of hydrothermal reaction of silk waste at 1:20 silk to water ratio at 160 degrees C. For the hydrothermal decomposition of fibroin, the highest protein yield was 0.455 mg protein/mg silk fibroin (1:100, 220 degrees C, 10 min) and that of amino acids was 0.755 mg amino acids/mg silk fibroin (1:50, 220 degrees C, 60 min). The rate of silk fibroin decomposition could be described by surface reaction kinetics. The soluble reaction products were freeze-dried to obtain sericin and fibroin particles, whose conformation and crystal structure of the particles were shown to differ from the original silk materials, particularly in the case of fibroin, in which the change from beta-sheet conformation to alpha-helix/random coil was observed.     

Single column analysis of amino acids in protein hydrolysates utilizing the fluorescamine reaction

A system is described for the separation of the amino acids commonly found in protein hydrolysates at the picomole level using a single ion exchange column and for their quantitation by the fluorescamine (4-phenylspiro[furan-2 (3H),1′-phthalan]-3,3′-dione) reaction. Three sodium citrate buffers were required for the separation of the amino acids with an analysis time of approximately 3 hr. The amino acids in 1 μg of hydrolyzed bovine serum albumin were separated using a single ion exchange column and were detected in the effluent from the column by the fluorescamine assay. The results were compared with those obtained using a commercial amino acid analyzer and 150 μg of hydrolyzed bovine serum albumin. The chromatogram produced by the more sensitive analyzer utilizing the fluorescamine reaction to detect the amino acids compared favorably with the chromatogram produced by the commercial analyzer utilizing the ninhydrin reaction with the exception that the proline peak was missing. Proline and hydroxyproline fail to yield fluorescence on reaction with fluorescamine unless converted from imines to primary amines.     

Reactivity of the imino acids formed in the amino acid oxidase reaction.

The reactivity of the imino acids formed in the D- or L-amino acid oxidase reaction was studied. It was found that: (1) When imino acids reacted with the alpha-amino group of glycine or other amino acids, transimination yielded derivatives less stable to hydrolysis than the parent imino acids. In contrast, when imino acids reacted with the epsilon-amino group of lysine or other primary amines, transimination yielded derivatives more stable to hydrolysis than the parent imino acids. (2) Imino acids react rapidly with hydrazine and semicarbazide, forming stable hydrazones and semicarbazones. At pH 7.7, the rate of reaction of the imino acid analogue of leucine with semicarbazide was 10(4) times greater than that of the corresponding keto acid. The reaction of imino acids with these reagents is rapid enough to permit one to follow spectrophotometrically the amino acid oxidase reaction. Imino acids also reacted with cyanide to yield stable adducts. (3) The rate of hydrolysis of the imino acid analogue of leucine was independent of pH above pH 8.5. At lower pH values, the rate of hydrolysis increased with decreasing pH. At 25 degrees C and in the absence of added amino compounds, this imino acid had a half-life of 22 s at pH 8.5. Its half-life was 9.9 s at pH 7.9.     

Thermophilic anaerobic amino acid degradation: deamination rates and end-product formation

Anaerobic thermophilic degradation of several amino acids was studied in batch cultures using an inoculum from a steady-state semicontinuous enrichment culture. Experiments were done in the presence and absence of methanogenesis and known electron acceptors in the Stickland reaction. Methanogenesis was found to be crucial for the degradation of amino acids known to be oxidatively deaminated (leucine, valine and alanine). Other amino acids (serine, threonine, cysteine and methionine) were degraded under both methanogenic and non-methanogenic conditions. Degradation rates for these four amino acids were 1.3 to 2.2 times higher in cases where methanogenesis was active. The degradation rates of serine, threonine, cysteine and methionine were about twice as high as the rates of leucine, valine and alanine under methanogenic conditions. Inclusion of different electron acceptors, known to work in the Stickland reaction, did not enhance the degradation rates of any amino acid used nor did they alter the degradation patterns. Glycine was oxidatively deaminated to acetate, carbon dioxide, hydrogen and ammonium.     

炒焦对山楂中氨基酸含量的影响分析

为探索炒焦对山楂中氨基酸的影响及山楂炒焦过程中氨基酸的变化,对炒焦前后山楂中氨基酸含量的变化进行了分析.测定结果显示,炒焦前后山楂中氨基酸的种类不变,各种氨基酸含量变化不一;方差分析显示炒焦前后氨基酸的含量变化不显著,炒焦对山楂中氨基酸的影响较小.由于山楂在炒焦过程具备发生美拉德反应的物质基础和客观条件,推测山楂中的氨...     

Reactions between amino acid compounds and phenols during oxidation

Summary About 30 per cent of organic soil nitrogen can be hydrolized with HCl to amino acids; about 30 per cent is nonhydrolizable. In contrast to this high content of amino acid nitrogen is the small availability of the nitrogen to micro-organisms. In light of the theory proposing a reaction between the -amino group of amino acids or peptides and quinones formed during oxidation of lignin degradation products or other phenolic compound, different types of phenols were oxidized by phenolases in presence of amino acid compounds.It could be shown that the reaction of binding of nitrogen started at pH values higher than 6.5, and that only such phenols reacted which had no methoxylated hydroxyl groups. The reaction of some phenols during oxidation in presence of amino acids was accompanied by deamination and decarboxylation of the latter.The reaction products of phenols with amino acids were stable against hydrolysis. Using peptides it was found that all amino acids, except the N-terminal which is bound to oxidized phenols, could be hydrolyzed normally.With serum albumin it could be shown that there is a reaction with the amino group of the N-terminal amino acid and also with the -amino group of lysine residues with phenols during oxidation. The reacted protein seemed to be degraded normally with a protease ofBacillus subtilis.Guest Scientist as Fulbright Research Scholar from the Agronomy Department of the Iowa State University, Ames, Iowa, U.S.A.     

Formation of N-[2(3-Alkylpyrazin-2-on-l-yl)acyl]amino Acids or -peptides on Heating Tri- or Tetrapeptides with Glyoxal

The reaction of tri- and tetrapeptides with glyoxal at 100°C and pH 5.0 was studied. A series of new pyrazinone compounds was isolated from the reaction solutions of tri- and tetrapeptides with glyoxal: N-[2(3-alkylpyrazin-2-on-l-yl)acyl] amino acids (I) and 2-(3-alkyl- pyrazin-2-on-l-yl)aIkyl acids (II) from tripeptides, (I), (II) and N-[2(3~alkylpyrazin-2-on-l-y]) acyl]-dipeptides (III) from tetrapeptides. Their chemical structures were determined by UV, IR, MS and NMR spectroscopy.

Aldehydes and free amino acids were also detected as reaction products. The amino acids were proved to be derived from the C-terminals of the peptides. Reaction mechanisms for the reaction of tri- and tetrapeptides with glyoxal were also proposed.     

Direct Colorimetric Method for the Determination of Free Ammonia in Blood

In an attempt to develope a rapid and simple method for the colorimetric determination of free ammonia in blood, the conditions for the indophenol reaction, the direct application of it for the determination of blood ammonia, and the interferences of a number of substances for the color development, have been investigated. This color reaction was sensitive enough for the direct method, but must be done under the limiting conditions, for the interfereing substances are contained in blood. Interferences of many amino acids for the color development were observed, but the effects differed among different amino acids, and many of substances other than amino acids showed very little or no intereference. Under the conditions applied, neither the amino acids nor other substances in blood interfered the method.     

Formation of proline thiohydantoin with ammonium thiocyanate: progress towards a viable C-terminal amino-acid-sequencing procedure.

Pure amino acid thiohydantoins are required as reference standards for development of C-terminal-sequencing procedures based on thiohydantoin formation of the C-terminal amino acids of peptides and proteins. Proline thiohydantoin was prepared using a straightforward method involving reaction of acetylproline with ammonium thiocyanate. It was characterized by UV spectrophotometry, mass spectrometry and back-hydrolysis to the free amino acid. These data establish unequivocally that the thiocyanate procedure is applicable to proline as well as to the other common amino acids. This work also validates earlier claims that proline thiohydantoin can be prepared by reaction with thiocyanic acid.     

Reaction of β-propiolactone with amino acids and its specificity for methionine

1. The reactions of beta-propiolactone with amino acids were investigated under various conditions of pH and temperature to find those under which the reagent acted with specificity. 2. At pH9.0 and 22 degrees , after 15min. of reaction, at least 85% of each amino acid had reacted, methionine and cystine being the most reactive. 3. At pH7.0 and 22 degrees most amino acids reacted; methionine, cystine and histidine reacted almost entirely, and proline and lysine to a significantly smaller extent. 4. At pH3.0 and 22 degrees further specificity was obtained; methionine and cystine were the only reactive amino acids. 5. Reaction at pH3.0 and 0 degrees was specific for methionine; it was the only amino acid modified even after 145hr. of reaction.     

Amino acids as catalysts of the binding reaction of formaldehyde with adenine residue in polyadenylic acid

Binding of formaldehyde and amino acids (Gly, Lys and Leu) with poly(A), poly(G), and poly(C) has been investigated in comparison with treatment with formaldehyde alone. It was found that in the case of poly(A) amino acids were found to catalyze the N-hydroxymethylation reaction on exocyclic amino groups of adenine. For example, at 20 degrees C and pH 6.0 the rate of this reaction increased about 10 fold in the presence of glycine.     

Protein degradation during anaerobic wastewater treatment: derivation of stoichiometry

The stoichiometry of reactions that describe protein degradation in anaerobic treatment systems were investigated. A methodology was developed to describe protein degradation to organic acids using a single reaction step. The reactions for individual amino acid fermentation and their mediating organisms were reviewed. The dominant fermentation pathways were selected based on a number of assumptions. Using the amino acid content of a model protein, it was then possible to determine stoichiometric coefficients for each major organic acid product in the overall degradation of the protein. The theoretical coefficients were then compared to those determined from two experimental runs on a continuously-fed, well-mixed, laboratory-scale anaerobic wastewater treatment system. In general, the coefficients compared well thus validating the use of a single reaction step for the overall catabolic reaction of protein degradation to organic acids. Furthermore, even when the protein concentration in feed or the feed flow rate was doubled, the amino acid fermentation pathways were found to occur predominantly by only one pathway. Although the choice of Stickland reactions over uncoupled degradation provided good comparisons, an electron balance showed that only about 40% of the amino acids could have proceeded coupled to other amino acid reactions. Uncoupled degradation of the remaining amino acids must have relied on the uptake of hydrogen produced from these reactions by hydrogen-consuming methane bacteria.