Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: CAS:61-90-5 (leucine)
 60,841 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The selective cleavage of peptide bonds by a serine protease from skeletal muscle (SK-protease) was examined using glucagon and neurotensin as substrates. Among the peptide bonds cleaved in these substrates, the most susceptible were Phe-Thr-Ser, Tyr-Leu, Trp-Leu, and Tyr-Ile. These results indicate that the SK-protease hydrolyzed the carboxyl side of aromatic amino acid residues under the experimental conditions. When the amino acid on the carboxyl side of aromatic amino acid residues was serine, threonine or glutamic acid, these peptide bonds, such as Phe-Thr, Tyr-Ser, and Tyr-Glu, were not susceptible to another serine protease from small intestine (SI-protease) under the same experimental conditions. The peptide bond between the arginines of Pro-Arg-Arg-Pro in neurotensin was hydrolyzed by the SI-protease, but not by the SK-protease. Thus the specificity of the SK-protease differs from that of the SI-protease. These results suggest that the specificity of the hydrolytic action of the SK-protease is more like that of bovine chymotrypsin A than like that of porcine chymotrypsin C and of the SI-protease.
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PMID:Selective cleavage of peptide bonds by a serine protease from rat skeletal muscle. 70 Dec 36

Immunological methods were used to study the effect of fasting on the in vitro synthesis of amylase (EC 3.2.1.1) in rat exocrine pancreas. After 72 h of fasting, the amylase enzyme activity of the pancreas and the rate of amylase synthesis were reduced 50%. No significant change in the activities of trypsin or chymotrypsin were detected. The decrease in leucine incorporation in total pancreas protein was accounted for by the decreased amylase synthesis. No change in the rate of amylase breakdown was detected. These results indicate that the rate of synthesis of amylase is controlled by food intake and is not directly related to the tissue content of enzyme.
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PMID:The effect of fasting on the in vitro synthesis of amylase in rat exocrine pancreas. 84 96

1. The process by which the egg-yolk protein precursor vitellogenin is biosynthesized, assembled and secreted by Xenopus laevis (South African clawed toad) liver was studied. It was previously shown in other laboratories that vitellogenin contains the two egg-yolk proteins lipovitellin (mol.wt. 140 000) and phosvitin (mol.wt. 35 000). 2. Evidence is presented which shows that Xenopus liver microsomal fractions synthesize precursors of vitellogenin. These precursors were solubilized from the membranes with detergent and analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. This analysis indicated that there is only one precursor polypeptide, and this has mol.wt. approx. 200 000 +/- 20 000. This demonstrates that the egg-yolk proteins are translated as part of this larger polypeptide. 3. Experiments also demonstrate the existence of a microsomal proteinase which is able to cleave the precursor into smaller fragments. The nature of these fragments provided some indirect evidence that phosvitin and lipovitellin light chains are situated together within the precursor molecule. 4. These precursor data fit in well with structural studies on serum vitellogenin, since it has been shown that the latter protein consists of two identical subunits each with a mobility on sodium dodecyl sulphate/polyacrylamide gels identical with that shown by the microsomal precursor. This indicates that both the intracellular precursor and subunit of vitellogenin have similar (but not necessarily identical) molecular weights. 5. It was also shown that trypsin or chymotrypsin can cleave the serum vitellogenin into leucine- and serine-rich fragments which resemble lipovitellin and phosvitin respectively. Attention is, however, drawn to the fact that the serine-rich fragment is not identical with phosvitin, since it contains eight times more leucine than that expected for the authentic phosvitin molecule [Penning (1976) Ph.D. Thesis, University of Southampton].
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PMID:Studies on the biosynthesis, assembly and secretion of vitellogenin, an oestrogen-induced multicomponent protein. 84 74

The C-terminal undecapeptide of ovine prolactin, H-Leu-Asn-Cys-Arg-Ile-Ile-Try-Asn-Asn-Asn-Cys-OH possesses several structural features common to protein proteinase inhibitors, yet has no inhibitor properties. The undecapeptide is completely hydrolysed by trypsin (Arg-Ile bond) and by chymotrypsin (Tyr-Asn bond), with a proteolytic coefficient of approximately 3,000 M-1 sec-1 and 240 M-1 sec-1 respectively. On the basis of these results, a consideration of entropy, and studies by other workers, we agree with the view of Nishino et al. that the best models for small synthetic peptides with inhibitor properties would be those naturally-occurring inhibitors whose reactive site is located within a small disulphide loop.
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PMID:A study of proteinase inhibition by simulation of inhibitor reactive site regions: interaction of the C-terminal undecapeptide of ovein prolactin with some proteinases. 85 30

A phosphorylated polypeptide (E4) of molecular weight 5000-6000, has been isolated from bovine embryonic enamel by Bio-Gel P-10 gel filtration and DE-52 ion-exchange chromatography. The peptide contains three serine residues all of which are phosphorylated. All three O-phosphoserine residues are in glutamic acid-O-phosphoserine-tyrosine sequences that are distributed relatively evenly along the polypeptide chain. Although it was not possible to sequence the entire polypeptide chain directly by automatic peptide sequencing, a partial sequence and peptide map was constructed on the basis of the sequence and composition of peptides derived by cyanogen bromide, trypsin and chymotrypsin digestion. The presence of glutamic acid, tyrosine and leucine adjacent to and near the O-phosphoserine residues may be important in calcium binding and in mineralization.
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PMID:Isolation, characterization and partial amino acid sequence of a phosphorylated polypeptide (E4) from bovine embryonic dental enamel. 88 76

Two isoinhibitors (II and III-B) have been isolated from kidney bean (Phaseolus vulgaris L.) in a highly purified state. Both were active against trypsin and chymotrypsin to the same extent. Their amino acid composition is characterized by a high content of half-cystine, aspartic acid (or asparagine) and serine, by the absence of valine, methionine and tryptophan. Glycine and serine were N-terminal in II and III-B respectively. Both isoinhibitors have C-terminal leucine.
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PMID:[Isolation and properties of trypsin isoinhibitors from kidney beans]. 90 94

Effects of hydrogen-bonding interactions of amide groups on reactivity of esters to alpha-chymotrypsin were studied. Of the methyl esters studied, only that from acetyl-L-phenylalanine has k3 rate-limiting. In methyl beta-phenylpropionates an alpha-acetamido substituent increased k2 greater than 550 times, k3 approximately 5 times; an alpha-acetylclycyloxy substituent increased k2 approximately 2 times, k3 approximately 6 times, both in comparison with the alpha-acetoxy esters. Essentially all carboxamidomethyl esters studied have k3 rate-limiting; reactivity to hydroxide is only 4 times that of methyl esters. In alpha-substituted beta-phenylpropionates, carboxamido-methyl esters show k2 values greater than 110 times greater than 280 times, greater than 26 times, and 7 times the k2 values of the methyl esters for the alpha substituents, acetoxy, acetylglycyloxy, hydroxy, and hydrogen, respectively. In esters of alpha-acetamido acids, carboxamidomethyl esters show k2 values 44 times, greater than 110 times, greater than 12 times, and approximately 33 times the k2 values of the methyl esters of glycine, alanine, leucine, and phenylalanine, respectively. Cyanomethyl esters also had k3 rate-limiting. Hydrogen-bonding to the enzyme of either an alpha-acetamido group or a carboxamidomethyl group combined with bonding of the beta-aryl group, orients the hydrolyzing groups properly, increasing k2. Hydrogen-bonding of both alpha-acetamido and carboxamido-methyl groups is effective to a lesser degree. The amide group appears to have small effects on Ks as hydrogen bonding is balanced by desolvation. It is proposed that desolvation during bonding increases k2 and Ks.
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PMID:Carboxamidomethyl esters as reactive substrates for alpha-chymotrypsin. Orientational effects of hydrogen-bonding interactions. 94 6

Ten different group A streptococcal M-protein preparations purified by trichloroacetic acid precipitation and three M-protein preparations purified by cellulose chromatography were examined by SDS and polyacrylamide gel electrophoresis, and analyzed for amino acid composition and N-terminal amino acids. Fingerprinting (both tryptic and chymotryptic) was performed on the cellulose purified preparations of M1, M12, and M29 proteins which showed these proteins to be structurally related. Trypsin produced mas with 37 to 42 peptides, whereas chymotrypsin digestion resulted in 8 to 12 peptides, depending on the M-type. Sequencing was performed on the M12 protein and tentative identification of nine N-terminal amino acids made. Molecular weights of the cellulose and TCA-purified M-proteins were determined by SDS gel electrophoresis and chromatography on G-200 Sephadex, with comparable results, indicating followed the patterns established for M-proteins, with high concentrations of lysine, aspartic acid, glutamic acid, alanine, and leucine. All 10 proteins had L-alanine as their N-terminal amino acid. Evidence for a one way cross-reaction between type 1 and type 29 streptococci was also found.
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PMID:Characterization of group A streptococcal M-proteins purified by two methods. 96 21

Activities of hydrolytic enzymes on the surface of monkey kidney, canine kidney, L. FM3A and various tumor cells were determined and compared with those in the cell homogenate. Although aminopeptidase (EC 3.4.11.-) activities were always detected on the surface membrane in mammalian cells, trypsin, chymotrypsin and elastase activities were not detected while slight glycosidase activity was detected in a suspension of cultured cells. The activities of alanine-, leucine-, methionine- and phenylalanine-aminopeptidases were rather high but aminopeptidase A, proline-, valine-, glycyl propline dipeptidyl-and glycyl propyl leucine-tripeptidyl-aminopeptidases showed relatively low activities. Aminopeptidase activity was also demonstrated in the isolated membrane fractions. The specific activities of enzymes in these membrane fractions were not significantly greater than in cell homogenate so it was concluded that these enzyme activities were rather loosely bound to the cell membrane. Further evidence for the localization of the aminopeptidase activities on the cell surface was obtained by using glass-bead-bound substrate and detecting the release of the terminal residues. When bestatin, a specific inhibitor against aminopeptidase B and leucine aminopeptidase, was included in the assay system for the enzyme activities on the cell surface, the enzymes were commonly inhibited in all types of cells.
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PMID:Aminopeptidase activities on the surface of mammalian cells. 99 Mar 9

Fourteen 3-carboxypropionyl-tripeptide-p-nitroanilides of the general formula 3-carboxypropionyl-alanyl-alanyl-Y-p-nitroanilide (Y = glycine, norvaline, S-methylcysteine, valine, norleucine, S-ethylcysteine, methionine, leucine, isoleucine, phenylalanine, tyrosine, S-benzylcysteine, Calpha-phenylglycine, and proline) were synthesized and their cleavage by elastase, trypsin, and chymotrypsin (Km, kcat and kcat/Km) was determined. The significance of amino acid residues in the position of Y was evaluated firstly with respect to their structure (topographically), and secondly with respect to their free energy (thermodynamically). The alanine residue substrate was cleaved best by elastase, the phenylalanine substrate by chymotrypsin. Trypsin cleaved two substrates only, that is those containing a phenylalanine and a tyrosine residue. The optimum length of the elastolytic substrates was studied in a series of N-3-carboxypropionyl-(Ala)n-p-nitroanilides (n = 1, 2, 3, 4, 5), N-3-carboxypropionyl-(Gly)n-p-nitroanilides (n = 1, 2, 3), and in p-nitroanilides of fatty acids with two to seven carbon atoms. Elastase cleaved tri, tetra, and pentapeptides of alanine. p-Nitroanilides of the glycine series, as well as p-nitroanilides of fatty acids were not cleaved. 3-Carboxypropionyl-tetra-alanine-p-nitroanilide was the most suitable substrate so far found for elastase cleavage; it is not cleaved by trypsin nor chymotrypsin. The optimum distance between Y and the terminal anionic carboxyl residue was found to be 1.8 nm in elastolytic substrates.
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PMID:p-Nitroanilides of 3-carboxypropionyl-peptides. Their cleavage by elastase, trypsin, and chymotrypsin. 99 49


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