Phosphorylation coupled to glycolytic and oxidative metabolism in cerebral mitochondrial systems

Abstract

Two cerebral mitochondrial preparations capable of coupling the metabolism of glucose (or fructose) to net phosphorylative processes are described. The first (P-1) requires the addition of crude yeast hexokinase for net phosphorylation. The second carries out an active aerobic glycolysis without the crude yeast material. In its presence, however, aerobic glycolysis is inhibited and phosphorylative efficiency is increased. It is suggested that this represents a shunt from a less efficient glycolytic to a more efficient, oxidatively linked phosphate-transfer system. A large portion of the phosphorylative yield of these systems is coupled to oxidative metabolism. This is indicated by the inhibitory action of cyanide, pentobarbital, dinitrophenol, and anaerobiosis and by the ability of the P-2 system consistently to provide P O ratios above 1. In the P-2 system oxygen consumption, in the presence of DPNH and fluoride, is equivalent to the amount of DPNH added, and some net phosphorylation is obtained. This is considered a reflection of the ability of cerebral as well as liver mitochondria to couple the oxidation of DPNH to phosphorylative processes.