title: Formation of a covalent intermediate between alpha-chymotryspin and the B-chain of insulin during enzyme-catalyzed hydrolysis.
abstract: 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.
mesh_terms: D001665:Binding Sites; D002850:Chromatography, Gel; D002918:Chymotrypsin / Q000378:metabolism; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D007328:Insulin; D007700:Kinetics; D010084:Oxidation-Reduction; D011485:Protein Binding; D013462:Sulfur Radioisotopes
chemical_list: D007328:Insulin; D013462:Sulfur Radioisotopes; D002918:Chymotrypsin