Phospholipases C and sphingomyelinases: Lipids as substrates and modulators of enzyme activity

This review article deals with phospholipases C (PLC), sphingomyelinases (SMases) and related lipases. Bacterial PC-preferring PLC and PI-specific PLC, bacterial SMases and PLC/SMases, eukaryotic SMases and ceramide phosphorylinositol hydrolases are discussed. The aim of the review is to offer a coherent description of lipid-protein interactions for the above enzymes, considering that (a) the enzyme activity is influenced by the physical properties of the substrate lipid, (b) the enzyme activity is modulated by non-substrate lipids, (c) enzyme end-products often change the physical properties of the lipid matrix, hence the enzyme activity. This approach allows a certain degree of understanding of phenomena such as: latency periods (lag times), enzyme interfacial activation, effects of intrinsic lipid curvature and of overall bilayer curvature on enzyme activity, and enzyme-promoted vesicle aggregation and fusion.