Griffiths, D. E. and Roberton, A. M.. (1966) Energy-linked reactions in mitochondria : studies on the mechanism of the energy-linked transhydrogenase reaction. Biochimica et Biophysica Acta. Enzymology and Biological Oxidation, Vol.118 (No.3). pp. 453-464. ISSN 0926-6593

Abstract

1. The mechanism of both the energy-linked and non-energy-linked trans-hydrogenase reaction catalysed by submitochondrial particles from beef-heart mitochondria has been examined using 3H- and 14C-labelled pyridine nucleotides as substrates. 2. The energy-linked transhydrogenase reaction does not proceed via a net group transfer of either the adenine or nicotinamide moieties or of phosphate from one pyridine nucleotide to another. 3. Studies with 3H-labelled pyridine nucleotides show conclusively that in the energy-linked transhydrogenase reaction hydrogen is transferred directly from the A locus of NADH to the B locus of NADP+, i.e. the energy-linked transhydrogenase is an A:B transhydrogenase involving direct hydrogen transfer. 4. Studies on the non-energy-linked transhydrogenase show conclusively that the stereochemistry of the non-energy-linked reaction is identical to that of the energy-linked transhydrogenase reaction. 5. When the reaction is carried out in tritiated water there is only a low incorporation of tritium into NADPH thus confirming that the reaction is one involving direct hydrogen transfer.

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