ENDOGENOUS SUBSTRATE FOR NUCLEAR OXIDATIVE PHOSPHORYLATION

Inosine increased both the rate and level of ATP synthesis in isolated rat thymus nuclei. Adenine was rapidly incorporated into nuclear ATP but the hypoxanthine moiety of inosine was incorporated only slightly. Inosine enhanced incorporation of adenine into nuclear ATP. It was concluded that the effect of inosine resided in the ribose part. Inhibition of glycolysis with 20 mm fluoride resulted in accumulation of d-3-phosphoglycerate. This accumulation was increased by inosine and methylene blue, suggesting the operation of the pentose phosphate pathway in thymus nuclei. Since nuclei contain amounts of glucose and glycogen too small to support nuclear oxidative phosphorylation it is suggested that nuclear oxidative phosphorylation in isolated nuclei is supported at least partly by ribose metabolism. Possibly ribose originates from nuclear RNA and other nucleotides. © 1969.