Regulation of NAD and NADP synthesis in human red cell.

NAD is synthesized in red cell from nicotinic acid and PRPP through the formation of nicotinate mononucleotide and desamido-NAD. Synthesis of one mole of NAD requires two moles of ATP. NADP comes from NAD phosphorylation by NAD-kinase (EC.2.7.1.23). NAD and NADP analysis on a population with ATP level ranging from 800 to 2500 nmoles/ml red cells showed a close correlation between ATP and pyridine cofactors. Moreover, NADP level appeared to be dependent of the redox-state of NADP/NADPH couple. Subjects with low NADPH (G-6-PD) deficient red cells, Hb Köln) showed lower NADtot/NADPtot ratio, suggesting a NAD-kinase equilibrium shift toward NADP related to lower levels of the negative effector NADPH, as already described in rat liver.