Phosphate-transfer reactions of adenosine and inosine nucleotides

Abstract

Extracts of acetone-dried sheep brain and lysed mitochondria of sheep liver brought about the phosphate-transfer reaction: Inosine triphosphate (TIP) + adenosine monophosphate (AMP)[long dash]} adenosine diphosphate (ADP) + inosine diphosphate (IDP). Evidence is based on paper-chromatographic separation and quantitative determinations of the reactants, and on the distribution of radioactive phosphate. The reaction was reversible in sheep-liver mitochondria. The reaction is inhibited by ethylenediaminetetraacetate and sodium fluoride. ATP and IMP did not interact under conditions where ITP and AMP interacted. Apart from interacting, ITP and AMP enter other reactions. The observed changes in the concentration of nucleotides taking place on addition of ITP and AMP can be accounted for by the transphosphorylations, dephosphorylations and deamination; ITP + AMP = IDP + ADP, ITP + ADP = ATP + IDP, ITP = IDP + P, IDP = IMP + P, AMP = IMP + NH3. The changes taking place on addition of ADP and IDP are approximately, but not fully, accounted for by the reactions: ADP + IDP = ITP + AMP, 2ADP = ATP + AMP, IDP = IMP + P, AMP = IMP + NH3.