Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: CAS:38562-01-5 (U-14)
 95 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

L-Azetidine-2-carboxylic acid is the naturally occurring lower homologue of L-proline. Reticulocytes from anemic rabbits incubated with DL-[14-C]azetidine-2-carboxylic acid synthesized radiolabeled hemoglobin, which when isolated from cell lysates co-chromatographed with unlabeled hemoglobin on Sephadex G-100 columns. Amino acid analysis of hemoglobin from reticulocytes incubated with DL-[14-C]-azetidine-2-carboxylic acid suggested that the homologue was incorporated into hemoglobin intact and unaltered. Alternatively, another amino acid analogue, 1-aminocyclopentane-[1-14-C]carboxylic acid, which is purported to be a valine antagonist, was not incorporated into hemoglobin under these conditions. Incubation of reticulocytes with 1, 5, and 10 mM L-azetidine-2-carboxylic acid reduced L-[U-14-C]proline (0.10 mM) incorporation into hemoglobin by 25, 58, and 72%, respectively. Conversely, 1.45 and 145 muM L-proline reduced radiolabeled azetidine-2-carboxylic acid (0.8 mM) in corporation into hemoglobin by 45 and 92%, respectively. Incorporation of L-[U-14-C]leucine and L-[U-14-C]lysine (0.1 mM each) into hemoglobin was unaffected at these concentrations of L-azetidine-2-carboxylic acid. These results suggest that L-azetidine-2-carboxylic acid is incorporated into hemoglobin without reducing the rate of globin synthesis in rabbit reticulocytes in vitro. The alpha and beta chains of hemoglobin into which [14-C]azetidine-2-carboxylic acid had been incorporated in rabbit reticulocytes in vitro were resolved electrophoretically on sodium dodecyl sulfate-polyacrylamide gels. The ratio of total radioactivity in the alpha and beta chains separately extracted from gels was in good agreement with the known 7:4 ratio of prolyl residues in the respective chains. Autoradiograms of two-dimensional tryptic peptide maps of rabbit globin into which either [14-C]azetidine-2-carboxylic acid or [14-C]proline had been incorporated showed nearly identical patterns of radioactivity. These results suggest that azetidine-2-carboxylic acid substitutes specifically for prolyl residues during in vitro hemoglobin synthesis in rabbit reticulocytes.
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PMID:Incorporation of L-azetidine-2-carboxylic acid into hemoglobin in rabbit reticulocytes in vitro. 111 11

To assess whether the dipeptide N-epsilon-(gamma-L-glutamyl)-L-lysine (glutamyl-lysine) can serve as a nutritional source of lysine, we compared the growth of mice fed (a) an amino acid diet in which lysine was replaced by six dietary levels of glutamyl-lysine; (b) wheat gluten diets fortified with lysine; (c) a wheat bread-based diet (10% protein) supplemented before feeding with lysine or glutamyl-lysine (0, 0.75, 1.50, 2.25, and 3% lysine HCl-equivalent in the final diet), not co-baked and (d) bread diets co-baked with these levels of lysine or glutamyl-lysine. With the amino acid diet, the relative growth response to glutamyl-lysine was about half that of lysine. The effect of added lysine on the nutritional improvement of wheat gluten depended on both lysine and gluten concentrations in the diet. With 10 and 15% gluten, 0.37% lysine HCl produced a marked increase in weight gain. Further increase in lysine HCl to 0.75% proved detrimental to weight gain. Lysine HCl addition improved growth at 20 and 25% gluten in the diet and did not prove detrimental at 0.75%. For whole bread, glutamyl-lysine served nearly as well as lysine to improve weight gain. The nutritive value of bread crust fortified or not was markedly less than that of crumb or whole bread. Other data showed that lysine or glutamyl-lysine at the highest level of fortification, 0.3%, improved the protein quality (PER) of crumb over that of either crust or whole bread, indicating a possible greater availability of the second-limiting amino acid, threonine, in crumb. These data and additional metabolic studies with U-14-C glutamyl-lysine suggest that glutamyl-lysine, co-baked or not, is digested in the kidneys and utilized in vivo as a source of lysine; it and related peptides merit further study as a sources of lysine in low-lysine foods.
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PMID:Improvement in the nutritional quality of bread. 191 Feb 50

Fumarases in the mitochondrial and cytosolic fractions of rat liver were separately purified and crystallized. These two fumarases were not distinguishable in physicochemical, catalytic, or immunochemical properties. The sequences of seven amino acids in the C-terminal portions of the two fumarases were shown using carboxypeptidase P to be identical, i.e.-Val-Asp-Glu-Thr-Ala-Leu-Lys-. The amino acid sequence of the N-terminal portion of the mitochondrial fumarase was determined by the Edman method as Ala-Gln-Gln-Asn-Phe-Glu-Ile-Pro-Asp-, but that of the cytosolic fumarase could not be determined by the Edman method, since the N-terminal amino acid was blocked. The N-terminal amino acid of the cytosolic fumarase was identified as N-acetyl-alanine by analysis of the acidic amino acid produced by digestion of the enzyme protein with pronase E, carboxypeptidase A and B. Then the sequence of five amino acids in the N-terminal portion was determined by analyzing the acidic peptide obtained by limited proteolysis of the enzyme protein with carboxypeptidase A as Ac-Ala-Ser-Gln-Asn-Ser-. Peptide mapping of the tryptic peptides obtained from the mitochondrial and cytosolic fumarases showed no difference in the amino acid sequences of the two except in their N-terminal portions. The turnover rates of the mitochondrial and cytosolic fumarases were determined by injecting L-[U-14C]leucine into rat and following the decay of specific radioactivity incorporated into immunoprecipitates from the partially purified enzyme. The half-life of the cytosolic fumarase was estimated as 4.8 days from the decay curve of its specific radioactivity. The decay curve of the specific radioactivity of the mitochondrial fumarase, obtained after a single injection of L-[U-14]leucine, was quite unusual: its specific radioactivity remained constant for about 7 days after pulse labeling, and then decreased exponentially with a half-life of 9.7 days. Similar amounts of cytosolic and mitochondrial fumarase were found in the livers of the rat, mouse, rabbit, dog, chicken, snake, frog, and carp, respectively. Similar subcellular distributions of the enzyme were also found in the kidney, heart, and skeletal muscle of rats, and in hepatoma cells (AH-109A). However, in rat brain no fumarase activity was detected in the cytosolic fraction. Two putative precursor polypeptides of rat liver fumarase were synthesized when rat liver RNA was translated in vitro in a rabbit reticulocyte lysate system.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Mechanism of synthesis and localization of mitochondrial and cytosolic fumarases in rat liver. 381 85