The incorporation of 15N into adenine nucleotides and their formation from inosine monophosphate by skeletal-muscle preparations

Abstract

The distribution of Nl5 in the nucleotides of rabbit skeletal muscle after the administration of Nl5 ammonium citrate has been investigated. Incubation of inosine monophosphate with Nl5 aspartic acid in the presence of homogenates or extracts of acetone-dried powders made from skeletal muscle produced labelled adenine nucleotides. In these systems no amination of inosine monophosphate took place with ammonium chloride as the N source and glutamic acid was only very slightly effective. With muscle extracts practically all the isotope incorporated into the adenine nucleotides was- localized in the 6-amino group. N of both the purine ring and the 6-amino group of muscle adenine nucleotides was labelled after injection of [Nl5] ammonium citrate. Some properties of an aqueous extract of acetone-dried powder of muscle catalyzing ami-nation of inosine monophosphate by aspartic acid have been studied. A compound, highly labelled with Nl5; has been isolated from whole muscle and from muscle extracts after incubation with inosine monophosphate and aspartic acid. Those properties of this substance which have been studied are identical with those of adenylosuccinate.