Chemical structure and biochemical significance of lysolecithins from rat liver

Abstract

1. 1. Synthetic lecithins containing in 2-position a [14C]fatty acid constituent were found to be hydrolysed by rat-liver homogenates so as to form both 1-acyl-glycero-3-phosphorylcholine and 2-acyl-glycero-3-phosphorylcholine.

2. 2. A comparison of the fatty acid pattern of lysolecithin obtained from rat liver by thin-layer chromatography with the fatty acid composition of 1-acyl-glycero-3-phosphorylcholine prepared by breakdown of liver lecithin with snake venom phospholipase A (EC 3.1.1.4) suggested that two structurally isomeric lysolecithins occur.

3. 3. Phospholipase A degradation of lysolecithin from rat liver previously labelled with 32P demonstrated that, apart from 1-acyl-glycero-3-phosphorylcholine, 2-acyl-glycero-3-phosphorylcholine was also present. Hydrolysis of lysolecithin with phospholipase C (EC 3.1.4.3) and separation of the monoglycerides formed confirmed that rat-liver lysolecithin consists of two structural isomers.

4. 4. A combination of these findings with the results obtained by Lands and co-workers on the selective enzymic transacylation of isomeric lysophosphoglycerides allows a monoacyl-diacyl phospholipid cycle to be formulated. This mechanism is postulated to play a part in maintaining the liquid-crystalline state of membraneous lipids.