Role of lipid protrusions in the function of interfacial enzymes.

Secretory phospholipase A(2) (sPLA(2)) is a class of interfacially active enzymes that selectively hydrolyze lipid molecules organized at interfaces like membranes. We present a simple theoretical model that relates the sPLA(2) action to the protrusions of the lipid molecules. The model explains (1) the observed enhancement of enzymatic activity by lipids with flexible, neutral, water-soluble polymers linked to their head groups and (2) the lag-burst kinetics of sPLA(2). It yields qualitative predictions of the effect of the initial composition of the membrane, the molecular weight of the polymer, and the composition of the hydrolysis products.