Transhydrogenation in Root Tissue: Mediation by Carbon Dioxide.

The C(14)O(2) incorporated into organic acids by excised corn roots is released with an estimated halftime of 3 hours. Homogenates of root tissue can mediate these reactions by coupling, in series, phosphoenolpyruvate carboxylase, diphosphopyridine nucleotide malic dehydrogenase, phosphopyridine nucleotide malic dehydrogenase. An important consequence is the transfer of hydrogen from reduced diphosphopyridine nucleotide to triphosphopyridine nucleotide which is then reduced.