title: The bile acid-inducible baiF gene from Eubacterium sp. strain VPI 12708 encodes a bile acid-coenzyme A hydrolase.
abstract: The human intestinal Eubacterium sp. strain VPI 12708 has been shown to have a multistep biochemical pathway for bile acid 7alpha-dehydroxylation. A bile acid-inducible operon encoding 9 open reading frames has been cloned and sequenced from this organism. Several of the genes in this operon have been shown to catalyze specific reactions in the 7alpha-dehydroxylation pathway. The baiF gene from this operon was cloned, expressed in Escherichia coli, and found to encode a novel bile acid-coenzyme A (CoA) hydrolase. The subunit molecular mass of the purified bile acid-CoA hydrolase was calculated to be 47,466 daltons and the native enzyme had a relative molecular weight of 72,000. The K m and Vmax for cholyl-coenzyme A (CoA) hydrolysis was approximately 175 microm and 374 micromol/min per mg protein, respectively. The enzyme used cholyl-CoA, 3-dehydrocholyl-CoA, and chenodeoxycholyl-CoA as substrates. No hydrolytic activity was detected using acetyl-CoA, isovaleryl-CoA, palmitoyl-CoA, or phenylacetyl-CoA as substrates. Amino acid sequence database searches showed no significant similarity of bile acid-CoA hydrolase to other thioesterases, but significant amino acid sequence identity was found with Escherichia coli carnitine dehydratase. The characteristic thioesterase active site Gly-X-Ser-X-Gly motif was not found in the amino acid sequence of this enzyme. Bile acid-CoA hydrolase from Eubacterium sp. strain VPI 12708 may represent a new family of thioesterases.
authors.affiliation: Department of Microbiology/Immunology, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA 23298-0678, USA.
authors.forename: H Q
authors.initials: HQ
authors.lastname: Ye
authors.forename: D H
authors.initials: DH
authors.lastname: Mallonee
authors.forename: J E
authors.initials: JE
authors.lastname: Wells
authors.forename: I
authors.initials: I
authors.lastname: Björkhem
authors.forename: P B
authors.initials: PB
authors.lastname: Hylemon
mesh_terms: D000217:Acyltransferases; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D001647:Bile Acids and Salts / Q000378:metabolism / Q000494:pharmacology; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004790:Enzyme Induction / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005051:Eubacterium / Q000201:enzymology* / Q000235:genetics*; D005798:Genes, Bacterial; D006801:Humans; D006836:Hydro-Lyases / Q000235:genetics; D007422:Intestines / Q000382:microbiology; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009876:Operon; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D001647:Bile Acids and Salts; D017931:DNA Primers; D000217:Acyltransferases; C060278:crotonobetainyl-CoA carnitine coenzyme A transferase; D013869:Thiolester Hydrolases; C117493:bile acid-CoA hydrolase; D006836:Hydro-Lyases