Purification and characterization of bile acid-CoA:amino acid N-acyltransferase from rat liver.
An in vitro study of bile acid-CoA:amino acid N-acyltransferase activity of rat liver was undertaken in order to determine whether separate amino acid-specific enzymes catalyzed the formation of glycine and taurine conjugates of bile acids as postulated by others. Polyacrylamide gel electrophoresis of 200-fold purified enzyme localized the glycine- and taurine-dependent activities to a single band. Both activities were optimal at pH 7.8 and showed similar loss of activity at pH 6.0, pH 9.0, in the presence of 5,5'-dithiobis(2-nitrobenzoic acid), and at temperatures exceeding 50 degrees. With the purified fraction, Km for glycine was 31 mM and Km for taurine was 0.8 mM. Km for several bile acid-CoA substrates was approximately 20 micron and independent of the amino acid acceptor. Only amino acids with terminal alpha- or beta-amino groups were active as acyl acceptors. Acyl donors were limited to bile acid-CoA derivatives. The data support the conclusion that the rat has a single bile acid-CoA:amino acid N-acyltransferase. The substrate kinetics are consistent with previous observations that taurine conjugates predominate in rat bile at normal hepatocellular concentrations of glycine and taurine.
D000217:Acyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D000596:Amino Acids; D000818:Animals; D001646:Bile / Q000201:enzymology*; D002793:Cholic Acids; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D051381:Rats; D013379:Substrate Specificity
D000596:Amino Acids; D002793:Cholic Acids; D000217:Acyltransferases