Kinetics of the enzyme-vesicle interaction including the formation of rafts and membrane strain

Abstract

In cells, an appreciable part of enzymes is associated with lipid membranes. Academic experimental studies of the function of membrane enzymes (e.g., PLA(2) representing a prototype for interfacial enzymology) are often focused on the enzyme-vesicle interaction or, more specifically, on conversion of lipid forming the external leaflet of the vesicle membrane. The corresponding kinetics are complicated by many factors inherent to the interfacial physics and chemistry. The understanding of the relative role of such factors and how they should be quantitatively described is still limited. Here, we present the mean-field kinetic equations, taking the formation of rafts in the membrane and the product-induced membrane strain into account, and analyze various scenarios of lipid conversion. In particular, we scrutinize the conditions when the kinetics may exhibit a transition from a relatively long latency period to a steady-state regime with fast nearly constant reaction rate. Specifically, we discuss the likely role of the pore formation in the external lipid layer in this transition. The latter effect may be caused by the product-induced tensile strain in this layer.