KINETIC ISOTOPE EFFECTS OF DEUTERIUM OXIDE ON SEVERAL /cap alpha/- CHYMOTRYPSIN-CATALYZED REACTIONS
The kinetics of several reactions catalyzed by alpha chymotrypsin were determined in D/sub 2/O as solvent, and the results were compared with the kinetics of the same reactions in H/sub 2/O as solvent. By a suitable choice of substrates it was possible to estimate the effect of D/sub 2/O on the binding of the substrate to the enzyme, acylation of the enzyme, and deacylation of the acyl- enzyme intermediate. The substrate p-nitrophenyl trimethylicetate was used for studying the acylation reaction, and trans-cinnimoyl- alpha -chymotrypsin and trimethylacetyl- alpha -chymotrypsin were used for studying the deacylation reaction. A sizable isotope effect was observed for both the acylation and deacylation reactions L-tryptophan methyl ester were also compared in D/sub 2/O and H/sub 2/O and it was observed that at high substrate concentrations the limiting rate constant is greater in H/sub 2/O than in D/sub 2/O by a factor of 2.83. The results indicate a ratedetermining proton transfer in the catalytic steps of the enzymatic reaction. (auth)
- Research Organization:
- Illinois Inst. of Tech., Chicago
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-16-026999
- OSTI ID:
- 4820169
- Journal Information:
- Journal of the American Chemical Society (U.S.), Journal Name: Journal of the American Chemical Society (U.S.) Vol. Vol: 84; ISSN JACSA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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