Labelling Rates and Detection of Intermediates in Mitochondrial Phosphorylations and other Sequential Reactions

BASED on his observation that mitochondrial protein-bound phosphohistidine becomes maximally labelled with added radioactive inorganic phosphate before maximum labelling of the mitochondrial ATP is reached, Prof. Boyer concluded in 1963 that protein-bound phosphohistidine is an intermediate in respiratory-chain phosphorylation1. By the summer of 1964, it was generally accepted that phosphohistidine is not on the main pathway of synthesis of mitochondrial ATP, but on the relatively slow side-path catalysed by succinyl-CoA synthetase and nucleosidediphosphate kinase. We had already pointed out early in 1964 that the kinetics of the incorporation were inconsistent with Boyer's theory and supported phosphohistidine as an intermediate on a slow side-path2.