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)

Bovine adrenal tyrosine hydroxylase has been obtained in a form that is 85 to 90% pure. Sodium dodecyl sulfate-gel electrophoresis and density gradient centrifugation studies have established that the subunit molecular weight of the chymotrypsin-solubilized enzyme is 34,000. The presence of iron in the purified enzyme (0.50 to 0.75 mol of iron/mol of enzyme) has been established. Crude particulate tyrosine hydroxylase can be activated by the phospholipid, phosphatidyl-L-serine, or by exposure to enzymatic phosphorylating conditions. Both forms of activation lower the Km of the enzyme for its 2-amino-4-hydroxypteridine cofactor. By contrast, tyrosine hydroxylase that has been solubilized by chymotrypsin cannot be activated by either of these methods.
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PMID:Bovine adrenal tyrosine hydroxylase: purification and properties. 1 85

We recently identified a novel protein tyrosine kinase that specifically phosphorylates truncated pp60c-src (Mr = 53,000) at a tyrosine residue(s) distinct from its autophosphorylation site. In this study, we examined whether this enzyme phosphorylates intact pp60c-src (Mr = 60,000) and determined its phosphorylation site. Non-neuronal and neuronal forms of intact pp60c-src were separately purified from the membrane fraction of neonatal rat brain by sequential column chromatographies. The novel kinase phosphorylated tyrosine residues of both forms of intact pp60c-src. The phosphorylation occurred in parallel with autophosphorylation of pp60c-src, and in both forms the final stoichiometry estimated was quite similar to that of autophosphorylation (about 5%). The enzyme also phosphorylated pp60c-src in which the kinase activity had been destroyed by an ATP analogue, p-fluorosulfonylbenzoyl 5'-adenosine. The phosphorylation site of the non-neuronal form was analyzed by sequential peptide mapping with tosylphenylalanyl chloromethyl ketone-treated trypsin and alpha-chymotrypsin. Tryptic digestion of the phosphorylated pp60c-src yielded a unique phosphopeptide that cross-reacted with an antibody specific for the carboxyl-terminal sequence of chicken pp60c-src. Digestion of the phosphopeptide with chymotrypsin yielded a product that comigrated with a synthetic phosphopeptide corresponding to the carboxyl-terminal 15 residues of chicken pp60c-src. These results clearly indicate that the carboxyl-terminal sequence of rat pp60c-src is identical to that of chicken pp60c-src, and a tyrosine residue corresponding to chicken Tyr527 is the phosphorylation site. This phosphorylation resulted in a decrease in the enolase phosphorylating activity of pp60c-src. Kinetic experiments indicated that this decrease in activity was due to a decrease in the Vmax value of pp60c-src. These findings support our previous proposal that the novel tyrosine kinase acts as a specific regulator of pp60c-src in cells.
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PMID:A protein tyrosine kinase involved in regulation of pp60c-src function. 248 Mar 46

The hypothesis that the ADP-sensitive form of phosphorylated Na+, K+-ATPase contains occluded sodium ions has been tested by a procedure which involves (i) modifying the enzyme with alpha-chymotrypsin or N-ethylmaleimide (NEM) so that the ADP-sensitive form is more stable than it is in the native enzyme, (ii) phosphorylating the modified enzyme with ATP in the presence of labelled sodium ions, and (iii) forcing the phosphorylated enzyme rapidly through a cation-exchange column and measuring the labelled sodium in the effluent. The results show that ADP-sensitive phosphoenzyme prepared from alpha-chymotrypsin- or NEM-modified Na+, K+-ATPase is able to carry labelled sodium ions through a cation-exchange resin. This behaviour was not seen with native Na+, K+-ATPase or when phosphorylation was prevented by the omission of magnesium ions or by the substitution of adenylyl(beta, gamma-methylene)diphosphonate (AMP-PCP) for ATP. The occluded sodium ions were rapidly released when the phosphoenzyme was dephosphorylated by ADP. When alpha-chymotrypsin-modified enzyme was phosphorylated by ATP with 1 mM-sodium in the medium, close to three sodium ions were occluded per phospho group. The stoicheiometry at much lower sodium concentrations could not be determined satisfactorily. A consideration of the rate constants of the reactions thought to be involved in the occlusion of sodium and in the release of sodium from the occluded state shows that, so far as they are known, these constants are compatible with the hypothesis that the occluded-sodium form of the phosphoenzyme plays a central role in sodium transport through the pump.
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PMID:The occlusion of sodium ions within the mammalian sodium-potassium pump: its role in sodium transport. 608 5

By quantitative phosphorus determination on the single chains of human fibrinogen it is demonstrated that the covalently bound phosphorus of adult and fetal fibrinogen is exclusively located in the A alpha chain. The A alpha-chain of fetal fibrinogen contains about twice as much phosphorus as the adult A alpha-chain in the well known position of Ser 3 of fibrino-peptide A as well as in a hitherto unknown second position on the A alpha-chain. By consecutive cleavage of the A alpha-chains of fetal and adult fibrinogen with cyanogen bromide, trypsin, and chymotrypsin, separation of the resulting peptide mixtures and analysis for phosphorylated amino acids, this second phosphorylation site could be traced to Ser 345 of the A alpha-chain. There is only one sequence homology between the two now known in vivo phosphorylation sites of human fibrinogen, namely that the second amino acid to the carboxyl side of the phosphorylated Ser is Glu. The sequence specificity of the up to now unidentified protein kinase phosphorylating fibrinogen allows it to be classified as a member of the group of type-2 casein kinases or casein kinases TS.
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PMID:The location of a second in vivo phosphorylation site in the A alpha-chain of human fibrinogen. 671 96

1. The sites of chymotrypsin action on glyceraldehyde 3-phosphate dehydrogenase (D-glyceraldehyde 3-phosphate) : DNA+ oxidoreductase (phosphorylating), EC 1.2.1.12) was established; limited proteolysis by chymotrypsin results in lowering of the phosphorolytic activity of the enzyme without affecting its oxidative activity. 2. The low-molecular fraction of the chymotrypsin digest separated by Sephadex G-100 chromatography, was fractionated on Bio-gels. Determination of the amino acid composition of the nine peptides isolated, and of their amino acid sequence, permitted to relate cleavage of Leu-64, Trp-84, Leu-109, Leu-141, Phe-165, Lys-212, Val-239, Leu-242, Leu-271 (or Phe-315) bonds in the enzyme to the decrease of the phosphorolytic activity.
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PMID:The sites of chymotrypsin action on the pig muscle glyceraldehyde 3-phosphate dehydrogenase during limited proteolysis. 726 78

The structural and functional properties of chloroplast glyceraldehyde-3-P-dehydrogenase I (D-Glyceraldehyde-3-phosphate: NADP oxidoreductase (phosphorylating) EC 1.2.1.13) from Spinacia oleracea were investigated by limited proteolysis. The enzyme is insensitive to trypsin and chymotrypsin, while Staphylococcus aureus V8 protease cleaves the C-terminal region of its subunits. Subunit A (36 kDa) is only partially cleaved at Glu 317. No intact subunit B (39 kDa) is found at the end of the proteolytic experiment: two forms are originated from this subunit which is cleaved at Glu 342 and Glu 320. Proteolytic cleavage at these sites does not significantly alter enzymatic activity, but leads to destabilization of the protein. Unlike the intact parent enzyme (600 kDa) the cleaved enzyme behaves as a 150-kDa species in size exclusion chromatography.
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PMID:Limited proteolysis of chloroplast glyceraldehyde-3-phosphate dehydrogenase (NADP) from Spinacia oleracea. 835 35

Phosphorus oxychloride (POCl(3)) is an intermediate in the synthesis of many organophosphorus insecticides and chemical warfare nerve gases that are toxic to insects and mammals by inhibition of acetylcholinesterase (AChE) activity. It was therefore surprising to observe that POCl(3), which is hydrolytically unstable, also itself gives poisoning signs in ip-treated mice and fumigant-exposed houseflies similar to those produced by the organophosphorus ester insecticides and chemical warfare agents. In mice, POCl(3) inhibits serum butyrylcholinesterase (BuChE) at a sublethal dose and muscle but not brain AChE at a lethal dose. In houseflies, POCl(3)-induced brain AChE inhibition is correlated with poisoning and the probable cause thereof. POCl(3) in vitro is selective for AChE (IC(50) = 12-36 microM) compared with several other serine hydrolases (BuChE, carboxylesterase, elastase, alpha-chymotrypsin, and thrombin) (IC(50) = 88-2000 microM). With electric eel AChE, methylcarbamoylation of the active site with eserine reversibly protects against subsequent irreversible inhibition by POCl(3). Most importantly, POCl(3)-induced electric eel AChE inhibition prevents postlabeling with [(3)H]diisopropyl phosphorofluoridate; i.e., both compounds phosphorylate at Ser-200 in the catalytic triad. Pyridine-2-aldoxime methiodide does not reactivate POCl(3)-inhibited AChE, consistent with an anionic phosphoserine residue at the esteratic site. The actual phosphorylating agent is formed within seconds from POCl(3) in water, has a half-life of approximately 2 min, and is identified as phosphorodichloridic acid [HOP(O)Cl(2)] by (31)P NMR and derivatization with dimethylamine to HOP(O)(NMe(2))(2). POCl(3) on reaction with water and HOP(O)Cl(2) have the same potency for inhibition of AChE from either electric eel or housefly head as well as the same toxicity for mice. In summary, the acute toxicity of POCl(3) is attributable to hydrolytic activation to HOP(O)Cl(2) that phosphorylates AChE at the active site to form enzymatically inactive [O-phosphoserine]AChE.
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PMID:Phosphoacetylcholinesterase: toxicity of phosphorus oxychloride to mammals and insects that can be attributed to selective phosphorylation of acetylcholinesterase by phosphorodichloridic acid. 1089 98