Abstract

The effect of NADH, NAD+, NADPH, and NADP+ on succinate driven ATP synthesis of Mg-ATP submitochondrial particles and on ATP hydrolysis in soluble and particulate F1 from bovine heart was studied. Hydrolysis was inhibited competitively by all pyridine nucleotides when the concentration of Mg [gamma 32P]-ATP was varied between 0.1 mM to 3 mM, but NAD+ was less effective. Succinate driven ATP synthesis at various concentrations of ADP was also inhibited by the four pyridine nucleotides, but NADH was much more effective. Increasing concentrations of phosphate decreased the extent of the NADH induced inhibition of ATP synthesis. The effect of various parts of the NADH molecule on ATP synthesis was tested; the order of inhibition by these compounds was: NADH greater than ADP-ribose greater than NAD+ greater than NADPH greater than NADP+ greater than nicotinamide mononucleotide greater than nicotinamide.