The enzymatic formation of novel bile acid primary amides.

Academic Article

Abstract

  • Bifunctional peptidylglycine alpha-amidating monooxygenase (PAM) catalyzes the copper-, ascorbate-, and O(2)-dependent cleavage of C-terminal glycine-extended peptides and N-acylglycines to the corresponding amides and glyoxylate. The alpha-amidated peptides and the long-chain acylamides are hormones in humans and other mammals. Bile acid glycine conjugates are also substrates for PAM leading to the formation of bile acid amides. The (V(MAX)/K(m))(app) values for the bile acid glycine conjugates are comparable to other known PAM substrates. The highest (V(MAX)/K(m))(app) value, 3.1 +/- 0.12 x 10(5) M(-1) s(-1) for 3-sulfolithocholylglycine, is 6.7-fold higher than that for d-Tyr-Val-Gly, a representative peptide substrate. The time course for O(2) consumption and glyoxylate production indicates that bile acid glycine conjugate amidation is a two-step reaction. The bile acid glycine conjugate is first converted to an N-bile acyl-alpha-hydroxyglycine intermediate which is ultimately dealkylated to the bile acid amide and glyoxylate. The enzymatically produced bile acid amides and the carbinolamide intermediates were characterized by mass spectrometry and two-dimensional (1)H-(13)C heteronuclear multiple quantum coherence NMR.
  • Keywords

  • Bile Acids and Salts, Glycine, Glyoxylates, Kinetics, Mixed Function Oxygenases, Multienzyme Complexes, Oligopeptides, Oxygen Consumption, Substrate Specificity
  • Digital Object Identifier (doi)

    Author List

  • King L; Barnes S; Glufke U; Henz ME; Kirk M; Merkler KA; Vederas JC; Wilcox BJ; Merkler DJ
  • Start Page

  • 107
  • End Page

  • 117
  • Volume

  • 374
  • Issue

  • 2