PMID: 20851883

Authors:

Abbott DW, Gilbert HJ, Boraston AB

Title:

THE ACTIVE SITE OF OGL PROVIDES UNIQUE INSIGHTS INTO CYTOPLASMIC OLIGOGALACTURONATE BETA-ELIMINATION.

Journal:

J Biol Chem. 2010 Sep 17.

Abstract:

Oligogalactuonate lyases (OGLs, now also classified as pectate lyase family 22) are cytoplasmic enzymes found in pectinolytic members of Enterobacteriaceae, such as the enteropathogen Yersinia enterocolitica. OGLs utilize a beta-elimination mechanism to preferentially catalyze the conversion of saturated and unsaturated digalacturonate (GalA2) into monogalaturonate (GalA) and the 4,5-unsaturated GalA-like molecule, DKI. To provide mechanistic insights into the specificity of this enzyme activity we have characterized the OGL from Y. enterocolitica, YeOGL, on oligogalacturonides and determined its three-dimensional X-ray structure to 1.65 Angstroms. The model contains a Mn2+ atom in the active site, which is coordinated by three histidines, one glutamine, and an acetate ion. The acetate mimics the binding of the uronate group of galactourono-configured substrates. These findings, in combination with enzyme kinetics and metal supplementation assays, provide a framework for modeling the active site architecture of OGL. This enzyme appears to contain a histidine for the abstraction of the lower case Greek alpha-proton in the -1 subsite, a residue that is highly conserved throughout the OGL family and represents a unique catalytic base among pectic active lyases. In addition we present a hypothesis for an emerging relationship observed between the cellular distribution of pectate lyase folding and their distinct metal coordination chemistries.