d-myoInositol 1:2-cyclic phosphate 2-phosphohydrolase

Abstract

1. An enzyme in extracts of mammalian tissues catalyses the hydrolysis of d-myoinositol 1:2-cyclic phosphate (an intermediary in the enzymic degradation of phosphatidylinositol) to produce d-myoinositol 1-phosphate. 2. The enantiomorph of the substrate is not attacked. 3. The pH optimum is about 8.1–8.3 and the reaction is stimulated by Mg²⁺ ions. 4. Extracts from rat kidney cortex and medulla are very rich sources of the enzyme; brain, testis and small intestine contain intermediary activities, and other tissues contain very small amounts.