ABSTRACT
The catabolism of phosphatidylcholine (PC) and other phospholipids is carried out by phospholipases. A short-chain PC molecule in a micelle has conformational, dynamic, and packing features analogous to those of naturally occurring PCs in bilayers. A special type of unilamellar vesicle forms spontaneously by adding 20 mol% short-chain PC to long-chain phospholipid multibilayers. The resultant PC has a head group on average parallel to the interface and a pronounced kink at the beginning of the sn-2 chain. The terminal water-soluble catabolic product choline is an inhibitor of glycerol-phosphocholine phosphodiesterase and will affect PC degradation at that level. The concept of PC accessibility, which involves area of the polar head group per molecule or motional uncoupling of the substrate PC from other neighboring PC molecules, may extrapolate directly to membrane-bound phospholipases. The short-chain PC in a micellar matrix is an excellent substrate for phospholipases.
