Mutation of His465 alters the pH-dependent spectroscopic properties of Escherichia coli glutamate decarboxylase and broadens the range of its activity toward more alkaline pH.

ABSTRACT: Glutamate decarboxylase (GadB) from Escherichia coli is a hexameric, pyridoxal 5'-phosphate-dependent enzyme catalyzing CO(2) release from the alpha-carboxyl group of L-glutamate to yield gamma-aminobutyrate. GadB exhibits an acidic pH optimum and undergoes a spectroscopically detectable and strongly cooperative pH-dependent conformational change involving at least six protons. Crystallographic studies showed that at mildly alkaline pH GadB is inactive because all active sites are locked by the C termini and that the 340 nm absorbance is an aldamine formed by the pyridoxal 5'-phosphate-Lys(276) Schiff base with the distal nitrogen of His(465), the penultimate residue in the GadB sequence. Herein we show that His(465) has a massive influence on the equilibrium between active and inactive fo

SUBMITTER: Pennacchietti E 

PROVIDER: S-EPMC2797229 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature