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.