Functional identification of the general acid and base in the dehydration step of indole-3-glycerol phosphate synthase catalysis.

ABSTRACT: The tryptophan biosynthetic enzyme indole-3-glycerol phosphate synthase is a proposed target for new antimicrobials and is a favored starting framework in enzyme engineering studies. Forty years ago, Parry proposed that the enzyme mechanism proceeds through two intermediates in a series of condensation, decarboxylation, and dehydration steps. X-ray crystal structures have suggested that Lys-110 (numbering according to the Sulfolobus solfataricus enzyme) behaves as a general acid both in the condensation and dehydration steps, but did not reveal an efficient pathway for the reprotonation of this critical residue. Our mutagenesis and kinetic experiments suggest an alternative mechanism whereby Lys-110 acts as a general acid in the condensation step, but another invariant residue, Lys-53, act

SUBMITTER: Zaccardi MJ 

PROVIDER: S-EPMC3772182 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature