Bhowmik_2007_J.Biol.Chem_282_36377

Reference

Title : The molecular basis for inhibition of BphD, a C-C bond hydrolase involved in polychlorinated biphenyls degradation: large 3-substituents prevent tautomerization - Bhowmik_2007_J.Biol.Chem_282_36377
Author(s) : Bhowmik S , Horsman GP , Bolin JT , Eltis LD
Ref : Journal of Biological Chemistry , 282 :36377 , 2007
Abstract :

The microbial degradation of polychlorinated biphenyls (PCBs) by the biphenyl catabolic (Bph) pathway is limited in part by the pathway's fourth enzyme, BphD. BphD catalyzes an unusual carbon-carbon bond hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA), in which the substrate is subject to histidine-mediated enol-keto tautomerization prior to hydrolysis. Chlorinated HOPDAs such as 3-Cl HOPDA inhibit BphD. Here we report that BphD preferentially hydrolyzed a series of 3-substituted HOPDAs in the order H > F > Cl > Me, suggesting that catalysis is affected by steric, not electronic, determinants. Transient state kinetic studies performed using WT BphD and the hydrolysis-defective S112A variant indicated that large 3-substituents inhibited His-265-catalyzed tautomerization by 5 orders of magnitude. Structural analyses of S112A:3-Cl HOPDA and S112A:3,10-diF HOPDA complexes revealed a nonproductive binding mode in which the plane defined by the C atoms of HOPDA's dienoate moiety is nearly orthogonal to that of the proposed keto tautomer observed in the S112A:HOPDA complex. Moreover, in the 3-Cl HOPDA complex, the 2-hydroxo group is moved by 3.6 A from its position near the catalytic His-265 to hydrogen bond with Arg-190 and access of His-265 is blocked by the 3-Cl substituent. Nonproductive binding may be stabilized by interactions involving the 3-substituent with non-polar side chains. Solvent molecules have poor access to C6 in the S112A:3-Cl HOPDA structure, more consistent with hydrolysis occurring via an acyl-enzyme than a gem-diol intermediate. These results provide insight into engineering BphD for PCB degradation.

PubMedSearch : Bhowmik_2007_J.Biol.Chem_282_36377
PubMedID: 17932031
Gene_locus related to this paper: burxl-bphD

Related information

Substrate HOPDA-3,10-DiF    HOPDA-3-Cl    HOPDA    HODA-6-phenyl
Gene_locus HOPDA-3,10-DiF    HOPDA-3-Cl    HOPDA    HODA-6-phenyl    burxl-bphD
Family HOPDA-3,10-DiF    HOPDA-3-Cl    HOPDA    HODA-6-phenyl    burxl-bphD    Carbon-carbon_bond_hydrolase
Structure HOPDA-3,10-DiF    HOPDA-3-Cl    HOPDA    HODA-6-phenyl    burxl-bphD    Carbon-carbon_bond_hydrolase    2RHW    2RHT

Citations formats

Bhowmik S, Horsman GP, Bolin JT, Eltis LD (2007)
The molecular basis for inhibition of BphD, a C-C bond hydrolase involved in polychlorinated biphenyls degradation: large 3-substituents prevent tautomerization
Journal of Biological Chemistry 282 :36377

Bhowmik S, Horsman GP, Bolin JT, Eltis LD (2007)
Journal of Biological Chemistry 282 :36377