Open AccessStructural and mechanistic analysis of trans ‐3‐chloroacrylic acid dehalogenase activity
Author(s) -
Pegan Scott D.,
Serrano Hector,
Whitman Christian P.,
Mesecar Andrew D.
Publication year - 2008
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444908034707
Subject(s) - dehalogenase , chemistry , active site , stereochemistry , residue (chemistry) , covalent bond , adduct , catalysis , halogenation , molecule , substrate (aquarium) , enzyme , organic chemistry , oceanography , geology
Trans ‐3‐chloroacrylic acid dehalogenase (CaaD) is a critical enzyme in the trans ‐1,3‐dichloropropene (DCP) degradation pathway in Pseudomonas pavonaceae 170. This enzyme allows bacteria to use trans ‐DCP, a common component in commercially produced fumigants, as a carbon source. CaaD specifically catalyzes the fourth step of the pathway by cofactor‐independent dehalogenation of a vinyl carbon–halogen bond. Previous studies have reported an X‐ray structure of CaaD under acidic conditions with a covalent modification of the catalytic βPro1 residue. Here, the 1.7 Å resolution X‐ray structure of CaaD under neutral (pH 6.5) conditions is reported without the presence of the covalent adduct. In this new structure, a substrate‐like acetate molecule is bound within the active site in a position analogous to the putative substrate‐binding site. Additionally, a catalytically important water molecule was identified, consistent with previously proposed reaction schemes. Finally, flexibility of the catalytically relevant side chain αGlu52 is observed in the structure, supporting its role in the catalytic mechanism.