Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Kinetic studies have been carried out of the monomer-dimer interaction of insulin, beta-lactoglobulin, and alpha-chymotrypsin using stopped-flow and temperature-jump techniques. The pH indicators bromothymol blue, bromophenol blue, and phenol red were used to monitor pH changes associated with the monomer-dimer interaction. In all three cases a kinetic process was observed which could be attributed to a simple monomer-dimer equilibrium, and association (k1) and dissociation (k-1) rate constants were determined. The results obtained are as follows: for insulin at 23 degrees C, pH 6.8, 0.125 M KNO3, k1 = 1.14 X 10(8) M-1 s-1, k-1 - 1.48 X 10(4)s(-1); for beta-lactoglobulin AB at 35 degrees C, pH 3.7, 0.025 M KNO3, d1 = 4.7 X 10(4) M-1 s-1, k-1 = 2.1 s-1; for alpha-chymotrypsin at 25 degreesC, pH 4.3, 0.05 M KNO3 k1 - 3.7 X 10(3) M-1 s-1, k-1 - 0.68 s-1. The kinetic behavior of the separated beta-lactoglobulin A and B was similar to that of the mixture. In the case of chymotrypsin, bromophenol blue was found to activate the enzyme catalyzed hydrolysis of p-nitrophenyl acetate, and a rate process was observed with the temperature jump which could be attributed to a conformational change of the indicator-protein complex. The association rate constant for dimer formation of insulin approaches the value expected for a diffusion-controlled process, while the values obtained for the other two proteins are below those expected for a diffusion-controlled reaction unless unusally large steric and electrostatic effects are present.
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PMID:A kinetic study of protein-protein interactions. 0 11

We differentiate indirect and direct methods. The indirect methods include the examination of the blood (ESR, blood picture, electrolytes, especially calcium, for the exclusion of hyperparathyroidism, status of fat and liver enzymes, activity of alpha-amylase and lipase. More informative than a serum determination is the measurement of the amylase activity in the 24-hour urine. The detection of chymotrypsin in the stool can be recommended as an investigative test also for use in general practive in collaboration with a central laboratory.- The direct methods include investigation of the duodenal juice with measurement of pH, bicarbonate, of the activities of chymotrypsin, trypsin, lipase and amylase. For excluding of a disturbance of the carbohydrate metabolism in addition to blood sugar determinations, glucose tolerance and tolbutamide tests, the determination of insulin activity is indicated.
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PMID:[Chemical Investigation of Chronic Pancreatitis]. 0 30

A cationic polypeptide growth factor, isolated from human serum and purified to homogeneity, has stimulated the replication of density-inhibited BALB/c 3T3 cells. It has a molecular weight of 1.3 x 10(4) daltons and an isoelectric point of 9.7. Trypsin or chymotrypsin digestion reduces the growth-stimulatory activity by 75%, whereas 2-mercaptoehanol completely abolishes it. The growth factor is heat-stable (100 degrees C X 10 min) and free of insulin-like activity. The highly purified serum growth factor has been labeled with 125I, and an antiserum to the growth factor was produced in the rabbit. A specific, highly sensitive radioimmunoassay has been developed. Factors with growth-stimulating activity have also been detected in human platelets and human pituitary gland extracts. Platelets and pituitary glands have antigenic determinants that are recognized by antibodies to the serum growth factor. The platelet and pituitary gland growth factors are also cationic and heat stable, and are destroyed by 2-mercaptoethanol. Thus the human serum, platelet, and pituitary gland growth factors have similar properties.
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PMID:Growth factors derived from human serum, platelets, and pituitary: properties and immunologic cross-reactivity. 8 59

The binding and the velocity of degradation of 125I-insulin in the absence or presence of varying concentrations of native procline insulin were studied using isolated rat hepatocytes. At insulin concentrations ranging from 5 X 10(-11) to 10(-6) M, insulin degradation velocity showed a first order dependence on the total concentration of insulin bound at steady state. The overall reaction had an apparent rate constant of 0.030 +/- 0.011 min-1. Furthermore, the degradation of a given amount of 125I-insulin bound to cells was more rapid and extensive than the degradation of the same amount of insulin which had been newly exposed to fresh cells. Mid pretreatment of isolated hepatocytes with trypsin or chymotrypsin at concentrations of 5 to 20 mug/ml depressed to the same degree the amount of 125-I-insulin bound at steady state and the 125I-insulin degradation velocity. Peptide or protein hormones unrelated to insulin, including the oxidized A and B chains of insulin, failed to depress the amount of insulin bound or the velocity of insulin degradation when present at concentrations of 10-5 or 10-6 M. Over a wide range of concentrations, various synthetic insulin analogues and naturally occurring insulins depressed to the same degree the amount of 125I-insulin bound at steady state and the 125I-insulin degradation velocity. These observations suggest that insulin bound to hepatocyte plasma membranes is the substrate for insulin degradation by the liver.
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PMID:Binding and degradation of 125I-insulin by rat hepatocytes. 17 97

The reaction between alpha-chymotrypsin (EC 3.3.21.1) and the B-chain of bovine insulin was studied radiochemically, by using the 3 5S-labelled sulfo B-chain. After incubation at pH 8.0, interrupted by the addition of trichloroacetic acid, a radioactive product was isolated from the reaction mixture. The labelled product was eluted in parallel with the enzyme in gel chromatography, and its properties at different H+ concentrations indicated that chemically it was an ester, i.e. a covalent enzyme-substrate intermediate. No interaction between sulfo beta-chain and alpha-chymotrypsinogen or phenyl-methyl sulfonyl fluoride-inhibited alpha-chymotrypsin was obtained during identical conditions.
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PMID:Formation of a covalent intermediate between alpha-chymotryspin and the B-chain of insulin during enzyme-catalyzed hydrolysis. 23 3

Two proteinases (proteinases I and II) have been purified from Crotalus adamanteus venom to the stage of electrophoretic homogeneity and proteinase II has been crystallized. The proteinase differ slightly in molecular weight and amino acid composition. Both are metalloenzymes requiring Zn2+ or Ca2+, or both; neither requires thiol compounds for activation. The proteinases are free of esterolytic activity against benzoly-L-arginine ethyl ester and benzoyl--tyrosine ethyl ester. Proteinase II cleaves the oxidized B chain of insulin at the bonds Phe1-Val2, His5-Leu6, His10-Leu11, Ala14-Leu15, Leu15-Tyr16, and Tyr-16-Leu17. Digestion of polylsine and polyarginine by proteinase II liberates products ranging from dodecapeptides to hexapeptides. Proteinases I and II catalytically inactive human plasma alpha 1-proteinase inhibitor (54,000 daltons). Electrophoretic analysis of the reaction of proteinase II with alpha 1-proteinase inhibitor reveals that an inactivated inhibitor species of 50,000 daltons is formed, and a peptide of 4,000 daltons is released. The gradual disappearance of the native inhibitor results in the corresponding loss of inhibitory activity against trypsin and chymotrypsin.
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PMID:Purification and some properties of two proteinases from Crotalus adamanteus venom that inactivate human alpha 1-proteinase inhibitor. 30 70

1. The reactivities of phenylglyoxal (PGO), glyoxal (GO), and/or methylglyoxal (MGO) with several proteins, including ribonuclease A [EC 3.1.4.22] and its derivatives, alpha-chymotrypsin [EC 3.4.21.1], trypsin [EC 3.4.21.4], lysozyme [EC 3.2.1.17], pepsin [EC 3.4.23.1], rennin [EC 3.4.23.4], thermolysin, and insulin and its B chain, have been examined. From analyses of the reaction products, PGO was shown to be the most specific for arginine residues. GO and MGO also reacted rapidly with arginine residues, but they also reacted with lysine residues to a significant extent. A side reaction with N-terminal alpha-amino groups was observed with each of these reagents. 2. Two arginine residues out of four in ribonuclease A, two out of three in alpha-chymotrypsin, one out of two in trypsin, one out of two in pepsin, and one out of five in rennin appeared to react with PGO fairly rapidly, indicating a difference in the relative accessibility of these residues by the reagent. Extensive modification of the arginine residues by PGO occurred with RCM-derivatives of ribonuclease A and insulin B chain. The N-terminal isoleucine residues of alpha-chymotrypsin and trypsin appeared to be unreactive with PGO because of salt bridge formation with an aspartyl residue. The activity of alpha-chymotrypsin toward N-benzoyl-L-tyrosine ethyl ester and the lytic activity of lysozyme were lost rapidly on treatment with PGO, as in the case of ribonuclease A. Pepsin and rennin were only partially inactivated by reaction with PGO.
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PMID:Further studies on the reactions of phenylglyoxal and related reagents with proteins. 32 41

The hydration isotherms of alpha-chymotrypsin, lysozyme, pork insulin, pork pepsin and serum albumin were obtained by means of dynamic method. The values of BET-monolayers for processes of water sorption leads to (h) and desorption comes from (h) do not depend on the static or dynamic way of achieving of hydration equilibrium in spite of difference in the shape of isotherms. The values of comes from h for proteins with known tertiary structure (alpha-chymotrypsin, lysozyme and insulin) coinside with the number of exposed polar amino acid side chains. The lowering of leads to h values in comparison with comes from h is correlated with inability of omega-amido groups of Asn and Gln residues and of ion pair-forming residues to take part in the formation of sorptive BET-monolayer. These rules for the interpretation of hydration isotherms were used to evaluate the numbers of exposed and buried polar side chains in proteins with unknown tertiary structure--pepsin and serum albumin.
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PMID:[Isotherms of globular protein hydration under dynamic conditions]. 32 24

Poly(A)-containing mRNA isolated from the islets of Langerhans obtained from two species of fish, angler fish (Lophius americanus) and sea raven (Hemitripterus americanus), stimulated protein synthesis 16-fold in a wheat germ cell-free system. Characterization of the translation products by polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed a major polypeptide weighing 11,500 daltons that was specifically precipitated by an antibody against angler fish insulin. Partial sequence analysis of the amino terminal revealed that this polypeptide is preproinsulin, in which the amino terminus of proinsulin is preceded by either 23 (angler fish) or 25 (sea raven) amino acid residues. Translation of fish islet mRNA in a wheat germ cell-free system in the presence of dog pancreas microsomal membranes led to the correct cleavage of the nascent preproinsulin, resulting in the synthesis of authentic fish proinsulin, as verified by partial sequence analysis. Moreover, the synthesized fish proinsulin was segregated, presumably into the luminal space of the dog pancreas microsomal vesicles, because it was found to be resistant to proteolysis by added trypsin and chymotrypsin. Our data thus suggest that the mechanisms and information for the transfer of secretory proteins across the microsomal membrane are highly conserved during evolution.
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PMID:Cell-free synthesis of fish preproinsulin, and processing by heterologous mammalian microsomal membranes. 32 65

High concentrations of ethanol are effective in reducing the intermolecular cross-linking which predominates when the reactions of tetranitromethane with the carboxypeptidase inhibitor from potatoes, a chymotrypsin inhibitor also from potatoes, and insulin are carried out under standard conditions. Including reagents such as ethanol may be of general utility in the preparation of monomeric nitro-derivatives of hydrophobic, low-molecular-weight proteins.
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PMID:Nitration of polypeptides using ethanol in reaction buffers minimizes crosslinking. 39 12


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