Probing the Role of Active Site Water in the Sesquiterpene Cyclization Reaction Catalyzed by Aristolochene Synthase.

ABSTRACT: Aristolochene synthase (ATAS) is a high-fidelity terpenoid cyclase that converts farnesyl diphosphate exclusively into the bicyclic hydrocarbon aristolochene. Previously determined crystal structures of ATAS complexes revealed trapped active site water molecules that could potentially interact with catalytic intermediates: water "w" hydrogen bonds with S303 and N299, water molecules "w1" and "w2" hydrogen bond with Q151, and a fourth water molecule coordinates to the Mg(2+)C ion. There is no obvious role for water in the ATAS mechanism because the enzyme exclusively generates a hydrocarbon product. Thus, these water molecules are tightly controlled so that they cannot react with carbocation intermediates. Steady-state kinetics and product distribution analyses of eight ATAS mutants designe

SUBMITTER: Chen M 

PROVIDER: S-EPMC4879067 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature