Antichymotrypsin interaction with chymotrypsin. Reactions following encounter complex formation.

The Journal of Biological Chemistry
S A Nair, B S Cooperman

Abstract

Serpins, serine proteinase inhibitors, form enzymatically inactive, 1:1 complexes (denoted E*I*) with their target proteinases, that only slowly release I*, in which the P1-P1' linkage is cleaved. Recently we presented evidence that the serpin antichymotrypsin (ACT, I) reacts with the serine proteinase chymotrypsin (Chtr, E) to form an E*I* complex via a three-step mechanism, E + I <==> E .I <==> EI' <==> E*I* in which EI', which retains the P1-P1' linkage, is formed in a partly or largely rate-determining step, depending on temperature (O'Malley, K. H, Nair, S. A., Rubin, H., and Cooperman, B. S. (1997) J. Biol. Chem. 272, 5354-5359). Here we extend these studies through the introduction of a new assay for the formation of the postcomplex fragment, corresponding to ACT residues 359 (the P1' residue) to 398 (the C terminus), coupled with rapid quench flow kinetic analysis. We show that the E.I encounter complex of wild type-rACT and Chtr forms both E*I* and postcomplex fragment with the same rate constant, so that both species arise from EI' conversion to E*I*. These results support our earlier conclusion that the P1-P1' linkage is preserved in EI' and imply that E*I* corresponds to a covalent adduct of E and I, either acyl enz...Continue Reading

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Citations

Jun 23, 2011·The Journal of Biological Chemistry·Daniel C HoffmannSabine A Eming
Sep 17, 2004·Biochemical and Biophysical Research Communications·Un-Beom KangCheolju Lee
Oct 12, 2000·The Journal of Biological Chemistry·K M O'Malley, B S Cooperman
Feb 7, 2001·The Journal of Biological Chemistry·P Mellet, J G Bieth
Jan 12, 2002·The Journal of Biological Chemistry·Jong-Shik Shin, Myeong-Hee Yu

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