Effect of NADP-glycohydrolase on glucose-6-phosphate dehydrogenase.

Abstract

The action of NADPase on glucose-6-phosphate dehydrogenase from human erythrocytes and leukocytes and from the rat liver has been studied. The NADPase was partially purified from rat spleen mitochondria and from erythrocyte stroma. The G-6-P-DH was purified 1450 fold from erythrocytes, 333 fold from leukocytes and 379 fold from rat liver. NADPase added to G-6-P-DH preparations leads to an inactivation which increases as a function of the used concentrations. When equal amount of NADPase are added, both from stroma and from spleen, a similar inactivating effect on G-6-P- DH is obtained. On the other hand no proportionality was obtained between NADPase activity and inactivation of G-6-P-DH; no stronger inactivation than 80% was ever reached. Our results give evidence for the hypothesis that the inactivation of G-6-P-DH is due to the cleavage of the nicotinamide-ribose linkage which binds the two monomers. The presence of NADPHj, as it was found in the enzyme molecule, could explain the non-total inactivation which could he obtained.