The bile acid-inducible baiF gene from Eubacterium sp. strain VPI 12708 encodes a bile acid-coenzyme A hydrolase

• Published in: Journal of lipid research Vol. 40; no. 1; pp. 17 - 23
• Main Authors: Ye, H Q, Mallonee, D H, Wells, J E, Björkhem, I, Hylemon, P B
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01.01.1999
• Subjects: 7α-dehydroxylation; Acyltransferases; Amino Acid Sequence; Bacterial Proteins; Base Sequence; Bile Acids and Salts - metabolism; Bile Acids and Salts - pharmacology; Cloning, Molecular; DNA Primers - genetics; Enzyme Induction - drug effects; Escherichia coli - enzymology; Escherichia coli - genetics; Eubacterium - enzymology; Eubacterium - genetics; Genes, Bacterial; Humans; Hydro-Lyases - genetics; Intestines - microbiology; Kinetics; Medicin och hälsovetenskap; Molecular Sequence Data; Molecular Weight; Operon; secondary bile acid; Sequence Homology, Amino Acid; Substrate Specificity; Thiolester Hydrolases - biosynthesis; Thiolester Hydrolases - chemistry; Thiolester Hydrolases - genetics
• ISSN: 0022-2275
• DOI: 10.1016/S0022-2275(20)33335-6

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.