ALKALINE PHOSPHODIESTERASE-I RELEASE FROM EUKARYOTIC PLASMA-MEMBRANESBY PHOSPHATIDYLINOSITOL-SPECIFIC PHOSPHOLIPASE-C .4. THE RELEASE FROMCACIA-PORCELLUS ORGANS

1. Alkaline phosphodiesterase I release from organs of Cacia porcellus by the action of phosphatidylinositol-specific phospholipase C (PIPLC ) of Bacillus thuringiensis was studied. 2. A significant amount of al kaline phosphodiesterase I was released from both slices and homogenat e of the kidney and small intestine but not from the liver or pancreas . 3. The release of the enzyme from kidney brush border membranes was dependent on, or proportional to, the reaction time and the PIPLC conc entration. The enzyme release by PIPLC was suppressed when the PIPLC w as heat-inactivated before addition to the reaction mixture. This sugg ests that the enzyme release must be due to direct action of PIPLC on kidney brush border membranes. 4. The released alkaline phosphodiester ase I had a molecular weight of 240,000 and was activated by Mg2+, but strongly inhibited by EDTA, thiol reagents and 5'-nucleotide-containi ng compounds.