'''Crystal Structure of BphD, a C-C hydrolase from Burkholderia xenovorans LB400'''
===Crystal Structure of BphD, a C-C hydrolase from Burkholderia xenovorans LB400===
==Overview==
<!--
Kinetic and structural analyses of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) hydrolase from Burkholderia xenovorans LB400 (BphD(LB400)) provide insight into the catalytic mechanism of this unusual serine hydrolase. Single turnover stopped-flow analysis at 25 degrees C showed that the enzyme rapidly (1/tau(1) approximately 500 s(-1)) transforms HOPDA (lambda(max) = 434 nm) into a species with electronic absorption maxima at 473 and 492 nm. The absorbance of this enzyme-bound species (E:S) decayed in a biphasic manner (1/tau(2) = 54 s(-1), 1/tau(3) = 6 s(-1) approximately k(cat)) with simultaneous biphasic appearance (48 and 8 s(-1)) of an absorbance band at 270 nm characteristic of one of the products, 2-hydroxypenta-2,4-dienoic acid (HPD). Increasing solution viscosity with glycerol slowed 1/tau(1) and 1/tau(2) but affected neither 1/tau(3) nor k(cat), suggesting that 1/tau(2) may reflect diffusive HPD dissociation, and 1/tau(3) represents an intramolecular event. Product inhibition studies suggested that the other product, benzoate, is released after HPD. Contrary to studies in a related hydrolase, we found no evidence that ketonized HOPDA is partially released prior to hydrolysis, and, therefore, postulate that the biphasic kinetics reflect one of two mechanisms, pending assignment of E:S (lambda(max) = 492 nm). The crystal structures of the wild type, the S112C variant, and S112C incubated with HOPDA were each determined to 1.6 A resolution. The latter reveals interactions between conserved active site residues and the dienoate moiety of the substrate. Most notably, the catalytic residue His265 is hydrogen-bonded to the 2-hydroxy/oxo substituent of HOPDA, consistent with a role in catalyzing ketonization. The data are more consistent with an acyl-enzyme mechanism than with the formation of a gem-diol intermediate.
The line below this paragraph, {{ABSTRACT_PUBMED_16964968}}, adds the Publication Abstract to the page
(as it appears on PubMed at http://www.pubmed.gov), where 16964968 is the PubMed ID number.
-->
{{ABSTRACT_PUBMED_16964968}}
==About this Structure==
==About this Structure==
Line 32:
Line 36:
[[Category: Meta cleavage product hydrolase]]
[[Category: Meta cleavage product hydrolase]]
[[Category: Pcb degradation]]
[[Category: Pcb degradation]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 10:49:52 2008''
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 08:47:19 2008''
Revision as of 05:47, 29 July 2008
This article has been automatically seeded. Changes to this page should pertain to the PDB entry only and not to the protein or biomolecule in general.
Kinetic and structural insight into the mechanism of BphD, a C-C bond hydrolase from the biphenyl degradation pathway., Horsman GP, Ke J, Dai S, Seah SY, Bolin JT, Eltis LD, Biochemistry. 2006 Sep 19;45(37):11071-86. PMID:16964968
