1. The supernatant fraction of adult rat brain contains a diphosphoinositide kinase. 2. Formation of triphosphoinositide by the enzyme in the presence of ATP and Mg2+ ions was shown with labelled ATP or labelled diphosphoinositide. 3. The kinase was also activated by Ca2+, Mn2+ and Co2+ ions, but to a smaller extent than by Mg2+ ions. 4. In the presence of optimum Mg2+ ion concentration the enzyme was inhibited by Ca2+ ions. 5. Activity did not depend on thiol groups and the pH optimum was 7·3. 6. The dialysed supernatant fraction had no diglyceride kinase activity and negligible phosphatidylinositol kinase activity. 7. Triphosphoinositide phosphomonoesterase was present but showed little activity under the conditions used to assay the kinase. 8. Diphosphoinositide kinase was purified by ammonium sulphate fractionation, ethanol treatment and chromatography on Sephadex G-200. 9. This purification removed much of the triphosphoinositide phosphomonoesterase.
SLOANE -STANLEY (1953) first showed that brain homogenates hydrolysed inositol lipids. The further study of RODNIGHT (1956) suggested that two enzymes, a phosphomonesterase and a phosphodiesterase were present. Extracts of ox brain have yielded purified enzymes of both the monoesterase and diesterase type which attack triphosphoinositide (TPI) (DAWSON and THOMPSON, 1964; THOMPSON and DAWSON, 1964a, b).A method has now been developed (HENDRICKSON and BALLOU, 1964) for the preparation of a purer triphosphoinositide than was used by DAWSON and THOMPSON,
Recently several communications have been published implicating impaired 3′5′ cyclic adenosine monophosphate (cyclic AMP) metabolism as a causal factor in affective disorders (1, 3, 7, 8, 9, 11). In particular, the urinary excretion of cyclic AMP in manic patients is reported to be increased compared with that of normal subjects, whereas in depressed patients a decreased excretion has been observed (1, 7, 8, 9). These findings form the basis of a theory explaining the systemic and mental symptoms of affective disorders (1).
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