title: Stoichiometry of reactions of alpha 2-macroglobulin with trypsin and chymotrypsin.
abstract: The stoichiometry of the individual steps, i.e. polypeptide chain cleavage, hydrolysis of the putative thioester bond and conformational change, of the reaction between alpha 2-macroglobulin and trypsin or chymotrypsin was analysed. The chain cleavage was monitored by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, the thioester hydrolysis by both a spectroscopic and a fluorimetric technique and the conformational change by tryptophan fluorescence. A stoichiometry of close to 2:1 was obtained for all reactions. This finding indicates that the alpha 2-macroglobulin half-molecule is an independent functional unit of the inhibitor, within which co-operativity between the two subunits may occur.
mesh_terms: D002850:Chromatography, Gel; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D004228:Dithionitrobenzoic Acid; D004591:Electrophoresis, Polyacrylamide Gel; D008301:Maleimides; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013439:Sulfhydryl Reagents; D014361:Trypsin Inhibitors; D000511:alpha-Macroglobulins / Q000494:pharmacology
chemical_list: D008301:Maleimides; D013439:Sulfhydryl Reagents; D014361:Trypsin Inhibitors; D000511:alpha-Macroglobulins; C019347:N-(7-dimethylamino-4-methylcoumarinyl)maleimide; D004228:Dithionitrobenzoic Acid; D002918:Chymotrypsin