Steady‐State Kinetics of Mitochondrial Nicotinamide Nucleotide Transhydrogenase

The steady‐state kinetics of the nonenergy‐linked nicotinamide nucleotide transhydrogenase reaction catalyzed by submitochondrial particles from beef heart were investigated. From the relationship found between reaction velocities and concentrations of substrates, and from the observed of product inhibition, it is concluded that the reaction involves a ternary‐complex, Theorell‐Chance mechanism. Maximal velocities of the forward and reverse reactions, Michaelis constants for the four substrates, dissociation constants of the binary enzyme. substrate complexes, and rate constants of the partial reactions are calculated. The results are discussed in relation to earlier information concerning the mechanism of the reaction.