Fructose 1,6-bisphosphatase, a key gluconeogenic enzyme, has been found in brain, a primarily glycolytic organ. The enzyme has been purified to 95% homogeneity and is essentially specific for fructose 1,6-bisphosphate. No other bisphosphate or monophosphate except sedoheptulose 1,7-bisphosphate (20% of fructose bisphosphate) is a substrate. Contrary to other mammalian fructose 1,6-bisphosphatases the brain enzyme requires no divalent cation and is not inhibited by 5'-AMP. The existence of this enzyme in brain completes a pathway that may provide for regulation of glycolysis in that organ. BIBLIOGRAPHIC REFERENCE: Majumder, A.L. and Eisenberg, F., Jr.: Inhibition of glycolysis in brain by a phospholipid effect on the interconversion of fructophosphates. A possible regulatory control on utilization of glucose 6-phosphate. J. Biol. Chem. 251: 7149-7156, 1976.