Crystal structure and molecular mechanism of an aspartate/glutamate racemase from Escherichia coli O157

FEBS Lett. 2016 Apr;590(8):1262-9. doi: 10.1002/1873-3468.12148. Epub 2016 Apr 5.

Abstract

EcL-DER, the aspartate/glutamate racemase from the pathogen Escherichia coli O157, exhibits racemase activity for l-aspartate and l-glutamate. This study reports the crystal structures of apo-EcL-DER, the EcL-DER-l-aspartate and the EcL-DER-d-aspartate complexes. The EcL-DER structure contains two domains, forming pseudo-mirror symmetry in the active site. A unique catalytic pair consisting of Thr(83) and Cys(197) exists in the active site. The characteristic conformations of l-Asp and d-Asp in the active site provide a straight structural evidence for the racemization mechanism of EcL-DER. In addition, the diversity of catalytic pairs implies that PLP-independent amino acid racemases adopt various catalytic mechanisms and are classified into different subgroups.

Keywords: PLP-independent racemase; aspartate/glutamate racemase; crystal structure; racemization mechanism.

Publication types

  • Letter
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Isomerases / chemistry*
  • Amino Acid Isomerases / metabolism
  • Amino Acid Sequence
  • Biocatalysis
  • Catalytic Domain
  • Crystallography, X-Ray
  • Escherichia coli O157 / enzymology*
  • Stereoisomerism
  • Substrate Specificity

Substances

  • Amino Acid Isomerases
  • aspartate racemase
  • glutamate racemase