title: Crystal structure and molecular mechanism of an aspartate/glutamate racemase from Escherichia coli O157.
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.
authors.affiliation: College of Life Sciences, Hebei University, Baoding, China.
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.affiliation: College of Life Sciences, Hebei University, Baoding, China.
authors.forename: Yinliang
authors.initials: Y
authors.lastname: Ma
authors.affiliation: College of Life Sciences, Hebei University, Baoding, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.affiliation: College of Life Sciences, Hebei University, Baoding, China.
authors.forename: Yaqi
authors.initials: Y
authors.lastname: Cui
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Zenglin
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: College of Life Sciences, Hebei University, Baoding, China.
authors.forename: Xianjiang
authors.initials: X
authors.lastname: Kang
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D055162:Biocatalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019453:Escherichia coli O157 / Q000201:enzymology*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000591:Amino Acid Isomerases; C019749:aspartate racemase; C062292:glutamate racemase
keywords: PLP-independent racemase; aspartate/glutamate racemase; crystal structure; racemization mechanism