Unequivocal demonstration of fructose-1,6-bisphosphatase in mammalian brain.

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Abstract
Fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase; EC 3.1.3.11) was found in rat brain and identified unequivocally. The enzyme was purified to 95% homogeneity by standard procedures, including adsorption to a phosphocellulose column followed by elution with substrate. The purified enzyme exhibited a broad optimum above pH 7.6. Both fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate were substrates of this enzyme; the hydrolysis of the latter occurred at about 20% of the rate of the former, and the Km for fructose 1,6-bisphosphate is approximately 1.32 .times. 10-4 M. 5''-AMP, an inhibitor of other mammalian fructose-1,6-bisphosphatases, was without effect, and in further contrast with other enzymes there was no metal requirement for activity. Purified brain enzyme failed to crossreact with the antibody prepared against the purified liver fructose-1,6-bisphosphatase. Antiserum produced against the brain fructose-1,6-bisphosphatase quantitatively precipitated the enzyme activity and formed preciptin bands with preparations of brain fructose-1,6-bisphosphatase.