On the question of an electrokinetic requirement for phospholipase C action

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Abstract
The phospholipase C ofclostridium welchii (α toxin) has an absolute requirement for trace quantities of Ca2+. It attacks pure phosphatidylcholine particles (smectic mesophases) having a close-packed bilayer structure only when their surface zeta potential is made positive by the addition of certain divalent ions (e.g., Ca2+) to the aqueous phase or by the presence of low concentrations of long chain cations to the lipid. Alternatively, if the rotational freedom of individual phospholipid molecules is increased by the insertion of shortn-alkanols (e.g., hexanol) into the bilayer or when a monolayer of the substrate at an air/water interface is expanded, enzymic hydrolysis can occur without any requirement for a net positive charge on the surface.