BEHAVIOR OF α-SUBSTITUTED CYSTINES IN A CYSTATHIONASE SYSTEM AND IN A PYRIDOXAL PHOSPHATE MODEL SYSTEM

1967 ◽  
Vol 45 (10) ◽  
pp. 1595-1617 ◽  
Author(s):  
R. J. Thibert ◽  
J. F. G. Diederich ◽  
G. W. Kosicki
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Hydrogen Atom ◽  
Absorption Spectra ◽  
Pyridoxal Phosphate ◽  
Copper Ions ◽  
Model System ◽  
Enzymatic System ◽  
Sulfur Amino Acids ◽  
Natural Substrate

The behavior of several new α-substituted cystines synthesized in this laboratory (α-methyl-, α-ethyl-, α-n-propyl-, α -n-butyl-, α-isopropyl-, and α-phenyl-DL-cystine) was studied in a cystathionase system and in a pyridoxal phosphate model system.The substituted cystines were neither cleaved by cystathionase nor were they degraded in the model system consisting of pyridoxal phosphate with or without cupric ions. Under the latter conditions, L-cystine reacted even in the absence of added metal. Copper ions, however, increased the rate of degradation of the amino acid. The α-hydrogen atom was apparently required for reactivity.The enzymatic system with cystathionase, isolated from rat liver and purified to some extent, was inhibited competitively by L-cystine and the substituted sulfur amino acids. Inhibition by the natural substrate, L-cystine, was greatest.In the non-enzymatic system, the substituted amino acids formed reactive Schiff bases whose absorption spectra were determined. The rates of formation of these addition compounds were followed spectrophotometrically.

Wool growth and sulfur amino acid entry rate in sheep fed roughage based diets supplemented with bentonite and sulfur amino acids

1989 ◽  
Vol 40 (4) ◽  
pp. 889 ◽  
Author(s):  
PD Fenn ◽  
RA Leng
Keyword(s):  
Amino Acids ◽  
Drinking Water ◽  
Amino Acid ◽  
Continuous Infusion ◽  
Basal Diet ◽  
Sulfur Amino Acid ◽  
Sulfur Amino Acids ◽  
Entry Rate ◽  
Wool Growth ◽  
Water Supplementation

In two experiments, sheep were offered a roughage-based diet supplemented with either cysteine or bentonite as a solid, or bentonite, cysteine or methionine added to their drinking water. Supplementation with cysteine as a solid had no effect on wool growth, while supplementation via drinking water had no effect on wool growth or cysteine entry rate into the blood. Supplementation with methionine via drinking water increased the entry rate of methionine into blood by 69% (P< 0.05) as measured by a continuous infusion of [35S]-methionine. This coincided with subsequent increases in wool growth of 16% (P< 0.05) compared to sheep fed a basal diet alone. Compared with the basal diet alone, supplementation with 30 g/day bentonite as a dry powder or 60 g/day as a suspension in drinking water increased wool growth by 19 and 20% respectively. Bentonite given as sole supplement did not increase the entry rate of either cysteine or methionine into the blood of sheep. When bentonite and sulfur amino acids were complexed or mixed, wool growth was not increased above that for bentonite or the amino acid alone.

scholarly journals Total 4EBP1 Is Elevated in Liver of Rats in Response to Low Sulfur Amino Acid Intake

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Angelos K. Sikalidis ◽  
Kevin M. Mazor ◽  
Minji Kang ◽  
Hongyun Liu ◽  
Martha H. Stipanuk
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dietary Treatment ◽  
Binding Activity ◽  
Initiation Factor ◽  
Sulfur Amino Acid ◽  
Sulfur Amino Acids ◽  
Protein Levels ◽  
Cellular Stresses

Translation initiation is known to be regulated by the binding of eukaryotic initiation factor 4E (eIF4E) by binding proteins (4EBPs), and there is evidence that amino acid deprivation and other cellular stresses upregulate 4EBP1 expression. To pursue the question of whether diets limited in an essential amino acid lead to induction of 4EBP1 expression in vivo, diets that varied in methionine and cystine content were fed to rats for 7 days, and 4EBP1 mRNA and protein levels and 4EBP1 phosphorylation state were determined. Total 4EBP1 mRNA and protein abundance increased in liver of rats with severely deficient intakes of sulfur amino acids (0.23% or 0.11% methionine without cystine) but not in animals with a less restricted intake of sulfur amino acids (0.11% methionine plus 0.35% cystine) but a similarly restricted intake of total diet (53 to 62% of control). The amount of 4EBP1 binding activity (α + β forms) was elevated in liver of rats fed sulfur amino acid-deficient diets, whereas the hyperphosphorylation of 4EBP1 was not affected by dietary treatment. Results suggest that changes in total 4EBP1 expression should be considered when examining mechanisms that attenuate protein synthesis during amino acid deficiency states.

scholarly journals The mechanism of action of serine transhydroxymethylase

1970 ◽  
Vol 116 (2) ◽  
pp. 277-286 ◽  
Author(s):  
P. M. Jordan ◽  
M. Akhtar
Keyword(s):  
Schiff Base ◽  
Amino Acid ◽  
Hydrogen Atom ◽  
Mechanism Of Action ◽  
Active Site ◽  
Enzyme Preparation ◽  
Pyridoxal Phosphate ◽  
Acid Oxidase ◽  
Amino Acid Oxidase

1. The preparation of stereospecifically tritiated glycines and the determination of their absolute configurations by the use of d-amino acid oxidase are described. 2. The reaction catalysed by serine transhydroxymethylase, which results in the conversion of glycine into serine, has been separated into at least four partial reactions. It is suggested that the first event in this conversion is the formation of a Schiff base intermediate of glycine and pyridoxal phosphate. The next important step involves the removal of the 2S-hydrogen atom of glycine to give a carbanion intermediate. Experiments pertinent to the mechanism of conversion of this carbanion intermediate into serine are described. 3. The enzyme preparation catalysing the conversion of glycine into serine also participates in the conversion of glycine into threonine and allothreonine. In both these conversions, glycine → serine and glycine → threonine, the 2S-hydrogen atom of glycine is eliminated and the 2R-hydrogen atom of glycine is retained. 4. In the light of these experiments the mechanism of action of serine transhydroxymethylase is discussed. It is suggested that methylenetetrahydrofolate is the carrier of formaldehyde, from which formaldehyde may be liberated at the active site of the enzyme, thus allowing the overall reaction to take place.

Effect of amino acid intake on brush-border membrane uptake of sulfur amino acids

1986 ◽  
Vol 251 (1) ◽  
pp. F125-F131
Author(s):  
R. W. Chesney ◽  
N. Gusowski ◽  
M. Padilla ◽  
S. Lippincott
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brush Border ◽  
Time Course ◽  
Brush Border Membrane ◽  
Sulfur Amino Acids ◽  
Beta Alanine ◽  
Renal Brush Border Membrane ◽  
Amino Acid Intake ◽  
Renal Brush Border

Alterations in the intake of sulfur amino acids (SAA) changes the rat renal brush-border membrane uptake of the beta-amino acid, taurine. A low-SAA diet enhances and a high-taurine diet reduces uptake (Chesney et al., Kidney Int. 24: 588-594, 1983). Neither the low-SAA diet nor the high-taurine diet alters the time course or concentration-dependent accumulation of the sulfur amino acids methionine and cystine or of inorganic sulfate. By contrast the uptake of beta-alanine, another beta-amino acid that competes with taurine, is greater in animals on the low-SAA diet. The high-taurine diet does not change beta-alanine uptake. The plasma levels of taurine are altered by dietary change, but not the values for methionine and cystine. This study indicates that renal adaptation is expressed for beta-alanine, a nonsulfur-containing beta-amino acid. By contrast, methionine, cystine, and sulfate, which participate in a variety of synthetic and conjugative processes, are not conserved by the renal brush-border surface following ingestion of either a low-methionine and -cystine diet or high-taurine diet.

Determination of Sulfur Amino Acids and Tryptophan in Foods and Food and Feed Ingredients: Collaborative Study

1988 ◽  
Vol 71 (3) ◽  
pp. 603-606
Author(s):  
Maryann C Allred ◽  
John L Macdonald
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Collaborative Study ◽  
Performic Acid ◽  
Cysteic Acid ◽  
Protein Hydrolysis ◽  
Sulfur Amino Acids ◽  
Feed Ingredients ◽  
Food And Feed

Abstract Samples of 4 foods, 1 animal feed, isolated soy protein, and 0-lao toglobulin were analyzed by 9 laboratories to determine concentrations of cysteine as cysteic acid, methionine as methionine sulfone, and tryptophan. Sulfur amino acids were determined by AOAC method 43.A08-43.A13 for food and feed ingredients, in which samples are oxidized with performic acid before protein hydrolysis with 6N HC1. Tryptophan was determined after protein hydrolysis with 4.2N NaOH. In both methods, free amino acids were separated by ionexchange or reverse-phase chromatography. Each laboratory was provided with detailed methods and with sealed vials containing solutions of standards. Samples were analyzed in duplicate, and variation between laboratories was determined. Coefficients of variation between laboratories for the 6 samples ranged from 5.50 to 11.8% for methionine as methionine sulfoxide, 8.59 to 17.3% for cysteine as cysteic acid, and 3.87 to 16.1% for tryptophan. Amino acid recoveries were determined by analysis of β-lactoglobulin and were based on expected levels of each amino acid obtained from amino acid sequence data. The mean recovery of cysteine was 97% with a range of 88-119%. For methionine, mean recovery was 98% (range 89-115%) and for tryptophan, 85% (range 59-102%). Method 43.A08- 43.A13 for food and feed ingredients has been adopted official first action for determination of cysteine and methionine in processed foods. The alkaline hydrolysis method has been adopted official first action for determination of tryptophan in foods and food and feed ingredients

scholarly journals The phtE Locus in the Phaseolotoxin Gene Cluster Has ORFs with Homologies to Genes Encoding Amino Acid Transferases, the AraC Family of Transcriptional Factors, and Fatty Acid Desaturases

1997 ◽  
Vol 10 (8) ◽  
pp. 947-960 ◽  
Author(s):  
Yuan Xin Zhang ◽  
Suresh S. Patil
Keyword(s):  
Amino Acids ◽  
Fatty Acid ◽  
Amino Acid ◽  
Binding Site ◽  
Pseudomonas Syringae ◽  
Pyridoxal Phosphate ◽  
Fatty Acid Desaturase ◽  
Transcriptional Factors ◽  
Copper Binding ◽  
Arac Family

A cluster of genes involved in the production of phaseolotoxin, a phytotoxin produced by Pseudomonas syringae pv. phaseolicola, contains eight (phtA through phtH) complementation groups (Y. X. Zhang, K. B. Rowley, and S. S. Patil, J. Bacteriol., 175:6451–6458, 1993). In this study, sequencing of the region encompassing the phtE locus revealed six putative open reading frames (ORFs), each preceded by a putative ribosomal binding site, and all oriented in the same direction. Reverse transcription-polymerase chain reaction suggested that the phtE locus is transcribed as one large (6.4 kb) transcript, indicating that the ORFs constitute an operon. Primer extension analysis showed that the transcript begins at a T, located 31 bp upstream of the ATG codon of ORF1. Comparison of the sequences of the putative ORFs with the sequences of known genes revealed that ORF3, encoding a protein containing 395 amino acids, has 55% similarity to the acetylornithine aminotransferase gene from Escherichia coli, and the ornithine aminotransferase genes from other organisms. A lysine residue that is a binding site for pyridoxal phosphate and an arginine residue that is a binding site for the α-carboxylate group of the substrate are conserved in ORF3. These data suggest that ORF3 encodes a protein involved in the biosynthesis of ornithine, a constituent of phaseolotoxin. ORF5, encoding a peptide of 378 amino acid residues, possesses a helix-turn-helix motif at the C-terminal end that is characteristic of the AraC family of transcriptional factors, and there is a possible leucine zipper at the N-terminal end of this peptide. ORF6, encoding a protein of 327 amino acids, has about 40% similarity with the fatty acid desaturase gene, desA, of Synechocystis Pcc6803 and considerable similarity with fatty acid desaturase genes from other organisms. ORF6 and desA show very similar hydropathy profiles and both contain a copper binding signature. Computer searches did not discover significant homologies in the data base for the other ORFs, but hydropathy analysis showed that all of them contain one to several hydrophobic domains, suggesting that the gene products of these ORFs may be membrane associated.

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