Stimulation of Fructose‐1,6‐Biphosphatase Activity and Synthesis in the Cerebral Cortex of Rats Submitted to the Convulsant Methionine Sulfoximine

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Abstract
Purification of rat cerebral cortex fructose‐ l,6‐biphosphatase (FBPase) was performed by substrate elution from phosphocellulose, followed by Sephadex G‐200 column filtration. The purified enzyme exhibited an optimum at pH 7.5, and its catalytic properties were very similar to those of the purified whole‐brain enzyme previously prepared by Majumder and Eisenberg in 1977. The isolated preparation was electrophoretically homogeneous. The molecular weight of the enzyme subunit was 40,000; the hydrophobic amino acids predominated with 592 residues, and tryptophan was not detected. Expressed as μmol fructose‐1,6‐biphosphate hydrolysed per g brain tissue wet weight per min, FBPase activity increased twofold 24 h after an intrapentoned injection of 100 mg per kg body weight of the convulsant methionine sulfoximine (MSO); the increase of the rate of incorporation of [1‐14C]valine into brain FBPase was 2.8‐fold under the same experimental conditions. A rabbit specific antiserum against rat cerebral cortex FBPase was prepared, and immunotitration studies confirmed both an increase in the number of molecules and the activation of brain FBPase, 24 h after administration of MSO. The increase of the number of brain FBPase molecules, induced by MSO, was due to an increase in synthesis of the enzyme, as shown by a double‐label valine incorporation study.