Characterization of the 4-hydroxybenzoyl-coenzyme A thioesterase from Arthrobacter sp. strain SU.
The Arthrobacter sp. strain SU 4-chlorobenzoate (4-CBA) dehalogenation pathway converts 4-CBA to 4-hydroxybenzoate (4-HBA). The pathway operon contains the genes fcbA, fcbB, and fcbC (A. Schmitz, K. H. Gartemann, J. Fiedler, E. Grund, and R. Eichenlaub, Appl. Environ. Microbiol. 58:4068-4071, 1992). Genes fcbA and fcbB encode 4-CBA-coenzyme A (CoA) ligase and 4-CBA-CoA dehalogenase, respectively, whereas the function of fcbC is not known. We subcloned fcbC and expressed it in Escherichia coli, and we purified and characterized the FcbC protein. A substrate activity screen identified benzoyl-CoA thioesters as the most active substrates. Catalysis of 4-HBA-CoA hydrolysis to 4-HBA and CoA occurred with a k(cat) of 6.7 s(-1) and a K(m) of 1.2 micro M. The k(cat) pH rate profile for 4-HBA-CoA hydrolysis indicated optimal activity over a pH range of 6 to 10. The amino acid sequence of the FcbC protein was compared to other sequences contained in the protein sequence data banks. A large number of sequence homologues of unknown function were identified. On the other hand, the 4-HBA-CoA thioesterases isolated from 4-CBA-degrading Pseudomonas strains did not share significant sequence identity with the FcbC protein, indicating early divergence of the thioesterase-encoding genes.
Department of Chemistry, University of New Mexico, Albuquerque, NM 87131, USA.
Zhihao
Z
Zhuang
Karl-Heinz
KH
Gartemann
Rudolf
R
Eichenlaub
Debra
D
Dunaway-Mariano
D000595:Amino Acid Sequence; D001173:Arthrobacter / Q000201:enzymology* / Q000235:genetics*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
D011994:Recombinant Proteins; C092167:4-hydroxybenzoyl-CoA hydrolase; D013869:Thiolester Hydrolases