PMID: 7372637Jun 10, 1980Paper

Kinetic characterization of cholyl-CoA glycine-taurine N-acyltransferase from bovine liver.

The Journal of Biological Chemistry
B Czuba, D A Vessey

Abstract

The bile acid-conjugating enzyme cholyl-coenzyme A:glycine/taurine N-acyltransferase previously purified from bovine liver was subjected to a bisubstrate kinetic analysis. Double reciprocal plots of reaction rates as a function of variable concentrations of aminoa acid and cholyl-CoA yielded the nonintersecting type of plots typical of ping-pong reaction mechanisms. A Tetra Uni ping-pong mechanism was supported by further kinetic analysis including demonstration that the enzyme will catalyze the release of CoA from cholyl-CoA without glycine being present. This half-reaction is shown not to be the result of an acyl-CoA thiolase contaminating the N-acyltransferase preparation. The specificity of the enzyme for amino acid was found to be quite narrow; no detectable rate was found for D-Ala, L-Ala, L-Ser, L-Glu-NH2, L-ornithine, or beta-alanine. Activity toward various acyl-CoA derivatives was also tested. Phenylacetyl-CoA, benzoyl-CoA, and acetyl-CoA were not substrates. CoA derivatives of the other common bile acids were very good substrates. Conjugated bile acids were efficient competitive inhibitors of cholyl-CoA binding. Cholic acid also inhibited; however, its inhibition pattern was complex. The enzyme could be reversibly in...Continue Reading

Related Concepts

Related Feeds

ASBMB Publications

The American Society for Biochemistry and Molecular Biology (ASBMB) includes the Journal of Biological Chemistry, Molecular & Cellular Proteomics, and the Journal of Lipid Research. Discover the latest research from ASBMB here.