Purification and characterization of bile acid-CoA:amino acid N-acyltransferase from human liver.

Academic Article

Abstract

  • The bile acid-conjugating enzyme, bile acid-CoA: amino acid N-acyltransferase, was purified 480-fold from the soluble fraction of homogenized frozen human liver. Purification was accomplished by a combination of anion exchange chromatography, chromatofocusing, glycocholate-AH-Sepharose affinity chromatography, and high performance liquid chromatography (HPLC) gel filtration. Following purification, the reduced, denatured enzyme migrated as a single 50-kDa protein band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A similar molecular mass was obtained for the native enzyme by HPLC gel filtration. Elution from the chromatofocusing column suggested an apparent isoelectric point of 6.0 (+/- 0.2). Using a rabbit polyclonal antibody raised against the purified enzyme, Western blot analysis using 100,000 x g human liver supernatant confirmed that the affinity-purified polyclonal antibody was specific for human liver bile acid-CoA:amino acid N-acyltransferase. The purified enzyme utilized glycine, taurine, and 2-fluoro-beta-alanine (a 5-fluorouracil catabolite), but not beta-alanine, as substrates. Kinetic studies revealed apparent Km values for taurine, 2-fluoro-beta-alanine, and glycine of 1.1, 2.2, and 5.8 mM, respectively, with corresponding Vmax values of 0.33, 0.19, and 0.77 mumol/min/mg protein. These data demonstrate that a single monomeric enzyme is responsible for the conjugation of bile acids with glycine or taurine in human liver.
  • Published In

    Keywords

  • Acyltransferases, Amino Acids, Animals, Birds, Blotting, Western, Cattle, Chromatography, High Pressure Liquid, Dogs, Electrophoresis, Polyacrylamide Gel, Humans, Hydrogen-Ion Concentration, Liver, Rats, Species Specificity, Temperature
  • Author List

  • Johnson MR; Barnes S; Kwakye JB; Diasio RB
  • Start Page

  • 10227
  • End Page

  • 10233
  • Volume

  • 266
  • Issue

  • 16