The reversible thiol-disulphide exchange of trypsin and chymotrypsinogen with a tumour-derived inhibitor. Kinetic data obtained with fluorescein-labelled polymeric collagen fibrils and casein as substrates.
Biochim Biophys Acta, 1979/5/10;568(1):49-58.
PMID: 444546
Abstract
Ehrlich ascites cells contain a cytoplasmic inhibitor of both trypsin and the granule neutral protease and possess a reactive thiol which interacts with an important disulphide bond in trypsin, resulting in the formation of the trypsin-inhibitor complex. When a fixed quantity of trypsin was completely inhibited by addition of the cytoplasmic inhibitor, the trypsin could be re-activated by the addition of either trasylol-trypsin or chymotrypsinogen. Since trasyloltrypsin, chymotrypsinogen (and any derived chymotrypsin) has no ability to solubilise fluorescein-labelled peptides from the substrate, the appearance of trypsin activity was probably due to a non-enzymic exchange reaction, in which these inactive forms displaced trypsin from the trypsin-inhibitor complex. Kinetic data suggest that this displacement was a time-dependent equilibrium reaction controlled by the relative concentration of the reacting species.
MeSH terms
Animals; Carcinoma, Ehrlich Tumor; Caseins; Chymotrypsinogen; Collagen; Disulfides; Fluoresceins; Kinetics; Mice; Peptide Hydrolases; Protease Inhibitors; Sulfhydryl Compounds; Trypsin
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