Selective Transfer of Cyclopropane Acids by Acyl Coenzyme A:Phospholipid Acyltransferases

Abstract

Abstract Coenzyme A thiol esters of the complete series of positional isomers of cis-methylene octadecanoic acid were synthesized. Their activities as substrates for acyl-CoA: phospholipid acyltransferases of rat liver microsomes were determined with positional isomers of acylglycerophosphoryl choline and acylglycerophosphoryl ethanolamine as acceptors. The results showed that the acyltransferases discriminated between the acyl-CoA isomers in quite different ways. Certain acyl-CoA esters were transferred at much different rates with different acylglycerophospholipid acceptors, suggesting that different enzymes were acting with the different acceptors. Comparison of the rates of cis-cyclopropane acid derivatives and cis-octadecenoic acid derivatives showed that the presence of π bonds in the acyl residue is not an important factor for the enzyme or enzymes transferring cis-acyl groups to the 1 position of acylglycerophospholipids. On the other hand, the presence of a π bond can cause higher or lower transfer rates to the 2-hydroxyl depending upon the location of the cis-functional group along the acyl chain.