Release of p-nitrophenyl phosphorylcholine-hydrolyzing phosphodiesterase from mouse brain membrane by phospholipase-C

p-Nitrophenyl phosphorylcholine-hydrolyzing phosphodiesterase activity, which is present more predominantly in brain than liver, kidney or small intestine, was released from the homogenate of brain membrane by Bacillus cereus phospholipase-C. The release of the enzyme was time-dependently induced selectively by phospholipase-C, but not by phospholipases A₂ or D, or protease. The released phosphodiesterase was partially purified by DEAE-sephacel and HPLC gel chromatographies with the specific activities of 400 and 1500 nmol/mg · h, respectively. The optimum pH and K_m values of the partially purified phosphodiesterase, possessing a mol. wt of 100,000, were observed to be pH 11 and 10 μM, respectively, quite similar to the values of the membrane-bound enzyme, except thermostability and temperature dependency of activity. Interestingly, among phosphorylcholine-containing compounds only glycero-phosphorylcholine exhibited the competitive inhibition of the phosphodiesterase activity.