The breakdown of adenosine triphosphate accompanying cholic acid activation by guinea-pig liver microsomes

Abstract

At low concentrations (0.005 [image]) of Mg2+ ion, the synthesis of cholyl-CoA by guinea-pig liver microsomes is accompanied by a release of inorganic ortho-phosphate from adenoslne triphosphate (ATP). This release is abolished by 0.015 [image] Mg2+. The inorganic pyrophosphatase of microsomes is strongly inhibited by Mg2+ in the presence, but not in the absence, of fluoride. ATP, adenosine diphosphate and ethylenediaminetetraacetic acid can activate the enzyme, probably by chelating Mg2+ ion, if fluoride is present. At a Mg2+ ion concentration of 0.015 [image], cholylhydroxamic acid synthesis is accompanied by a release of inorganic pyrophosphate though it was not possible to demonstrate an exact stoichiometry between them. The release of pyrophosphate is not dependent on the presence of hydroxylamine. These results and the synthesis of oligo-peptides in animal tissues are briefly discussed.