The BH1999 protein of Bacillus halodurans C-125 is gentisyl-coenzyme A thioesterase.
In this study, we have shown that recombinant BH1999 from Bacillus halodurans catalyzes the hydrolysis of gentisyl coenzyme A (CoA) (2,5-dihydroxybenzoyl-coenzyme A) at physiological pH with a k(cat)/K(m) of 1.6 x 10(6) M(-1) s(-1) and the hydrolysis of 3-hydroxybenzoyl-CoA with a k(cat)/K(m) of 3.0 x 10(5) M(-1) s(-1). All other acyl-CoA thioesters tested had low or no substrate activity. The BH1999 gene is juxtaposed with a gene cluster that contains genes believed to function in gentisate oxidative degradation. It is hypothesized that BH1999 functions as a gentisyl-CoA thioesterase. Gentisyl-CoA thioesterase shares the backbone fold and the use of an active site aspartate residue to mediate catalysis with the 4-hydroxybenzoyl-CoA thioesterase of the hotdog fold enzyme superfamily. A comparative study of these two enzymes showed that they differ greatly in the rate contribution made by the catalytic aspartate, in the pH dependence of catalysis, and in substrate specificity.
Zhuang
Zhihao
Z
Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA.
Song
Feng
F
Takami
Hideto
H
Dunaway-Mariano
Debra
D
D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology*; D002384:Catalysis; D005841:Gentisates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000302:isolation & purification; D013869:Thiolester Hydrolases / Q000235:genetics / Q000378:metabolism*
D005841:Gentisates; D011994:Recombinant Proteins; C092167:4-hydroxybenzoyl-CoA hydrolase; D013869:Thiolester Hydrolases