Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2066258 | Toxicon | 2006 | 6 Pages |
Abstract
The kinetic behavior of a thrombin-like enzyme from Lachesis muta muta venom has been studied with 13 tripeptidyl p-nitroanilide substrates. Eight substrates were unprotected at the N terminus and were used for the regression analysis of the experimentally determined kinetic parameters 1/Km, kcat and kcat/Km. The individual contribution of each amino acid side chain to the kinetic parameters was calculated. The amino acid sequence of the ideal substrate (D-Pro-Leu-Arg-pNA) was determined from a regression analysis for each kinetic parameter. This result was confirmed experimentally. The structural analysis of the tripeptides showed that the binding to the S3 sub-site had a small effect on Km. The binding of l-Leu to the S2 sub-site increased kcat without changing the value of Km. The analysis of the kinetic parameters revealed that, in the binding of l-Leu to the S2 sub-site, the enzyme bound the transition state configuration of the substrate/product transformation more tightly than that of the substrate.
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Authors
Henrique P.B. Magalhães, Arinos Magalhães, Luiz Juliano, David Lee Nelson, Edyr Rogana,