The overall objective of this work is to document the regulation of glycolysis in brain. The research encompasses two aspects of the objective: 1) a detailed study of the protein and/or phospholipid factors required for the binding of hexokinase to the mitochondrial membrane and 2) a study of the partitioning of hexokinase (HXK), phosphoglucose isomease (PGI), phosphofructokinase (PFK) and creatine kinase (CK) between mitochondria and cytosol as a function of the energy status of nerve cells. Hexokinase, solubilized from mitochondria by glucose-6-phosphate, has an apparent molecular weight of 13,000 daltons and is capable of binding to HXK-deficient mitochondria. The solubilized enzyme, chromatographically purified, has an apparent molecular weight of 100,000 daltons and is not capable of rebinding to mitochondria. Goals set for the next year are 1) to confirm the molecular weight difference and to document the factor(s) responsible for binding and 2) to complete our investigation of the influence of energy status of neuronal perikarya on the subcellular distribution of HXK and to extend these observations to PGI, PFK and CK.