[Activity of phosphoinositide-specific phospholipase C in rabbit nerves at rest and during stimulation]

The dependence of rabbit sciatic nerve PtdIns-specific phospholipase C activity Ca2+ and pH has been studied. The enzyme was found to hydrolyze PtdInsP2 in a Ca(2+)-dependent manner. The maximal activity was detected at 1mM CaCl2 for the cytosolic enzyme and at 0.1 mM CaCl2 for membrane-bound enzyme. The pH optima determined for the cytosolic and particulate enzymes were pH 6.0 and 7.0, respectively. The enzyme activity in the cytosolic fraction was shown to remain practically constant under nerve stimulation (200 impulses/sec, 5 min), whereas in microsomal fraction it was 44% greater compared to the resting nerve. It is suggested that the enzyme is bound to membrane in intact axon, therefore the rapid signal (depolarizing stimulus) transduction into axon becomes possible.