Binding and function of mitochondrial glycerol kinase in comparison with those of mitochondrial hexokinase

Mitochondrial-bound glycerol kinase in rat brain was examined with reference to factors involved in the binding and significance of the binding in relation to ATP metabolism inside the mitochondria. The mitochondrial-bound glycerol kinase was solubilized with glycerol 3-phosphate or ADP, and the solubilized enzyme was rebound to mitochondria by addition of divalent cations. The rebinding was decreased by the presence of glycerol 3-phosphate, while was increased by glucose 6-phosphate. Positive correlation was found between the formation of glycerol 3-phosphate by mitochondrial-bound glycerol kinase and ATP content in mitochondria in experiments using various concentrations of succinate and ADP. On the other hand, glycerol 3-phosphate formation was inhibited by addition of inhibitors for mitochondria functions, such as oligomycin, dinitrophenol, cyanide, and atractyloside. Furthermore, formation of dihydroxyacetone phosphate from glycerol was proved, indicating the involvement of glycerol kinase in glycerol phosphate shuttle in combination with glycerol phosphate dehydrogenase. These findings are discussed in comparison with those of mitochondrial-bound hexokinase.