A peptide corresponding to a potential polyphosphoinositide binding site of phospholipase C-β 2 enhances its catalytic activity

A peptide corresponding to a basic consensus amino acid motif present in both actin-binding proteins and phosphoinositide-specific phospholipases C was synthesized and its effect on the activity of a recombinant phospholipase C-β 2 (PLCβ 2) expressed in baculovirus-infected insect cells was studied. The peptide markedly and specifically stimulated the activity of the enzyme. This stimulatory effect required a particular primary and/or secondary structure of the peptide and occurred without lowering the affinity of the enzyme for Ca 2+. The function of the PLCβ 2 segment corresponding to the peptide might be to bind and offer the substrate to the catalytic domain of this enzyme in a more favorable configuration or, alternatively, to interact with a hypothetical inhibitory constraint.