Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Two bitter peptides, H-Phe-Tyr-Pro-Glu-Leu-Phe-OH (I) and H-Val-Glu-Val-Phe-Ala-Pro-Pro-Phe-OH (II) were isolated from casein, hydrolyzed by alpha-chymotrypsin. The hexapeptide is cleaved by thermolysine between Glu and Leu. The two fragments are bitter too. A bitter dodecapeptide (III) was obtained 20 min hydrolysis of casein with trypsin. On account of amino acid composition and N-terminus peptide III is probably identical with a peptide from a 12 hrs hydrolyzate, described in 1970 by Matoba. The peptides I and III have equal taste tresholds in the range of 0.08-0.10 muM/ml.
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PMID:[Bitter peptides of casein isolated by hydrolysis with alpha-chymotrypsin and trypsin (author's transl)]. 122 11

The synthetic cyclic tetrapeptide (L-Leu-L-Tyr-delta-Avaler-delta-Avaler) is an effective inhibitor of chymotrypsin, competitive with linear peptides like Ac-L-Leu-L-Tyr-OMe. An x-ray diffraction analysis of the crystal structure of the cyclic peptide shows that the conformation of the 18-membered ring is very similar to that of one of the four conformers of cyclic hexaglycyl. There is no internal hydrogen bonding. Side chains are located on two "corners" of the approximately rectangular ring. The chii1 angles for Leu and Tyr are -74 and -48 degrees, respectively. The Leu side chain is extended away from the polypeptide ring while the Tyr side chain is folded under an adjacent carbonyl bond. The cell parameters for the space group P2U are: a = 9.361 (3 A, b = 19.039 (10) A, c = 9.603 (3), A, and beta = 116.54 (3) degrees. A molecule of (CH3)2SO (disordered) and a molecule of H2O cocrystallized with the cyclic peptide.
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PMID:Conformation of cyclo-(L-Leu-L-Tyr-delta-Avaler-delta-Avaler), a synthetic inhibitor of chymotrypsin, by x-ray analysis. 124 91

The complete amino acid sequence of rat thyrocalcitonin has been determined by automated Edman degradations of the intact molecule, a cyanogen bromide fragment, and by degradations of mixtures of peptides produced by hydrolysis of the hormone with trypsin and chymotrypsin. The sequence determined was H2N-Cys-Gly-Asn-Leu-Ser-Thr-Cys-Met-Leu-Gly-Thr-Tyr-Thr-Gln-Asp-Leu-Asn-Lys-Phe-His-Thr-Phe-Pro-Gln-Thr-Ser-Ile-Gly-Val-Gly-Ala-Pro-NH2. This sequence differs in only two positions from that found in the human hormone, i.e. leucine-16 in the rat vs phenylalanine-16 in the human, and serine-26 in the rat vs alanine-26 in the human. These similarities and differences are consistent with the previously reported immunological properties of the hormones isolated from these two species.
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PMID:The complete amino-acid sequence of rat thyrocalcitonin. 127 75

A human urine serine proteinase chymotrypsin like hydrolyzes the peptide bonds: Phe-Ser (kinin); Gly-Gly, Leu-Arg, Phe-Lys (neuropeptides) and Gln-Gln (substance P). Endopeptidase H2 hydrolyzes better oligopeptides with 4 to 18 aminoacid residues than larger peptides, it does not hydrolyzes kininogen or proenkephalin. The enzyme behaves as an oligoendopeptidase.
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PMID:Further characterization of endopeptidase H2 a serine proteinase from human urine. 128 11

A series of fluorinated alpha-keto acid derivatives [PhCHFCOCO2R,PhCH2CHFCOCO2R,PhCF2-COCO2R, and PhCH2CF2COCO2R (R = H, Me, and Et)] was synthesized. They were inhibitors of chymotrypsin, with Ki values ranging from 4700 to 15 microM. Benzylpyruvic derivatives were generally more potent than the corresponding phenylpyruvic analogs. Esters of the first series were also more potent than their corresponding acids, and potency increased with the number of fluorine atoms. By replacing the ethoxy group of PhCH2CF2COCO2Et (15b) with an amino acid chain (i.e., alanyl-leucyl-arginine methyl ester hydrochloride and alanyl-leucyl-valine ethyl ester), the resultant peptides PhCH2CF2COCO-Ala-Leu-Arg-OMe.HCl.H2O (20) and PhCH2CF2COCO-Ala-Leu-Val-OEt.H2O (23) were found to be slow-binding inhibitors of chymotrypsin with considerably lower Ki values (0.19 and 3.6 microM, respectively). 19F NMR studies indicate, in the case of 20, the presence of an enzyme-inhibitor complex with a hemiketal structure similar to those observed between trifluoromethyl ketones and chymotrypsin. The results illustrate that effective protease inhibitors can be designed by enhancing the electrophilic character of the reactive carbonyl group (with an electron-withdrawing group placed on each side of the carbonyl group). Their potency and/or selectivity can also be improved by taking advantage of binding interactions at S' subsites of the protease.
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PMID:Inhibition of chymotrypsin by fluorinated alpha-keto acid derivatives. 132 15

Peptide synthesis was carried out in a variety of organic solvents with low contents of water. The enzyme was deposited on the support material, celite, from an aqueous buffer solution. After evaporation of the water the biocatalyst was suspended in the reaction mixtures. The chymotrypsin-catalyzed reaction between Z-Phe-OMe and Leu-NH2 was used as a model reaction. Under the conditions used ([Z-Phe-OMe]0 less than or equal to 40 mM, [Leu-NH2]0/([Z-Phe-OMe]0 = 1.5) the reaction was first order with respect to Z-Phe-OMe. Tris buffer, pH 7.8, was the best buffer to use in the preparation of the biocatalyst. In water-miscible solvents the reaction rate increased with increasing water content, but the final yield of peptide decreased due to the competing hydrolysis of Z-Phe-OMe. Among the water-miscible solvents, acetonitrile was the most suitable, giving 91% yield with 4% (by vol.) water. In water-immiscible solvents the reaction rate and the product distribution were little affected by water additions in the range between 0% and 2% (vol. %) in excess of water saturation. The reaction rates correlated well with the log P values of the solvent. The highest yield (93%) was obtained in ethyl acetate; in this solvent the reaction was also fast. Under most reaction conditions used the reaction product was stable; secondary hydrolysis of the peptide formed was normally negligible. The method presented is a combination of kinetically controlled peptide synthesis (giving high reaction rates) and thermodynamically controlled peptide synthesis (giving stable reaction products).
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PMID:Enzymatic peptide synthesis in organic media: a comparative study of water-miscible and water-immiscible solvent systems. 136 30

Loss of chymotrypsin binding capacity of alpha 2-macroglobulin in diabetic plasma on in vitro incubation, could be partially prevented by phenylmethyl sulphonyl fluoride and pepstatin A. Prior ten-fold dilution of plasma with 0.02 M phosphate buffer (pH 7.0) completely arrested the process. The phenomenon could not be reactivated by Ca2+, lecithin or bovine serum albumin. Diabetic plasma, like normal plasma, exhibited maximal hydrolytic activities on H-D-Pro-Phe-Arg-p-nitroanilide, H-D-Val-Leu-Arg-p-nitroanilide and H-D-Ile-Pro-Arg-p-nitroanilide. The hydrolytic activities were not significantly diminished on incubation of plasma at 37 degrees C for 12 hr, unlike alpha 2-macroglobulin activity. On gel chromatography on Sephadex G-200, part of the proteolytic activity in diabetic plasma coeluted with alpha 2-macroglobulin in the VO region. A second activity peak (absent in normal plasma) was eluted with a Ve/V0 value of 1.40. Possible role of free proteinases in diabetic plasma in the inactivation of alpha 2-macroglobulin is discussed.
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PMID:Further studies on proteinases and alpha 2-macroglobulin activity in diabetic plasma. 138 30

Poly-L-lysine with molecular masses of 3.3-290 kDa increased the amidolytic activities of leukocyte elastase and cathepsin G at low concentration, but had little effect on the activities of pancreatic elastase, alpha-chymotrypsin, plasmin and thrombin. Highly purified cathepsin G was obtained from column of EAH Sepharose 4B or Suc-L-Tyr-D-Leu-D-Val-pNA-Sepharose (affinity chromatography) by elution with poly-L-lysine solution (0.4 mg/ml, molecular weight (MW.) 290000 or 2.2 mg/ml, MW. 3300). Leukocyte elastase, adsorbed to Suc-L-Tyr-D-Leu-D-Val-pNA-Sepharose, was not eluted with poly-L-lysine solution. The amino acid composition of purified cathepsin G has been determined.
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PMID:Application of poly-L-lysine to purification of leukocyte cathepsin G by affinity chromatography. 139 85

The total synthesis of the insect neuropeptide derivative Z-Gly-Gly-Ser-Leu-Tyr-Ser-Phe-Gly-Leu-NH2 has been carried out by a convergent solid phase strategy. For the coupling of the N-terminal pentapeptide to the C-terminal tetrapeptide, three different methods were assayed. Racemization of the acyl activated amino acid during the fragment condensation reaction was monitored by HPLC. Best results were obtained by enzymatic coupling in a low water containing media using adsorbed alpha-chymotrypsin. An optically pure product was obtained in 82% yield after 1 h of reaction. Chemical methods such as DIC/HOBt and BOP/HOBt/NMM always rendered highly optically impure products containing 10-20% of the D-epimer.
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PMID:Racemization free coupling of peptide segments. Synthesis of an insect neuropeptide. 139 72

Matrix metalloproteinase 9 (MMP-9) has been purified as an inactive zymogen of M(r) 92,000 (proMMP-9) from the culture medium of HT 1080 human fibrosarcoma cells. The NH2-terminal sequence of proMMP-9 is Ala-Pro-Arg-Gln-Arg-Gln-Ser-Thr-Leu-Val-Leu-Phe-Pro, which is identical to that of the 92-kDa type IV collagenase/gelatinase. The zymogen can be activated by 4-aminophenylmercuric acetate, yielding an intermediate form of M(r) 83,000 and an active species of M(r) 67,000, the second of which has a new NH2 terminus of Met-Arg-Thr-Pro-Arg-(Cys)-Gly-Val-Pro-Asp-Leu-Gly-Arg-Phe-Gln-Thr- Phe-Glu. Immunoblot analyses demonstrate that this activation process is achieved by sequential processing of both NH2- and COOH-terminal peptides. TIMP-1 complexed with proMMP-9 inhibits the conversion of the intermediate form to the active species of M(r) 67,000. The proenzyme is fully activated by cathepsin G, trypsin, alpha-chymotrypsin, and MMP-3 (stromelysin 1) but not by plasmin, leukocyte elastase, plasma kallikrein, thrombin, or MMP-1 (tissue collagenase). During the activation by MMP-3, proMMP-9 is converted to an active species of M(r) 64,000 that lacks both NH2- and COOH-terminal peptides. In addition, HOCl partially activates the zymogen by reacting with an intermediate species of M(r) 83,000. The enzyme degrades type I gelatin rapidly and also cleaves native collagens including alpha 2 chain of type I collagen, collagen types III, IV, and V at undenaturing temperatures. These results indicate that MMP-9 has different activation mechanisms and substrate specificity from those of MMP-2 (72-kDa gelatinase/type IV collagenase).
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PMID:Matrix metalloproteinase 9 (92-kDa gelatinase/type IV collagenase) from HT 1080 human fibrosarcoma cells. Purification and activation of the precursor and enzymic properties. 140 Apr 81


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