Metabolism of lysophosphatidyl ethanolamine and lysophosphatidyl choline by homogenates of rabbit polymorphonuclear leukocytes and alveolar macrophages

Abstract

A comparison has been made between the conversion of (32)P-labeled lysophosphatidyl ethanolamine (LPE) and lysophosphatidyl choline (LPC) to their respective acylated and deacylated derivatives by homogenates of rabbit polymorphonuclear leukocytes and alveolar macrophages. Synthesis of PE by both homogenates and of PC by macrophage homogenates proceeded to about the same extent and is attributed to direct acylation of the lyso compounds. At higher LPC concentrations formation of PC by leukocytes is far greater than by macrophages. The mechanism of this enhanced synthesis of PC, which is brought out by higher substrate concentrations, is believed to be a transfer of the acyl group of one LPC molecule to another. Under optimal conditions macrophage homogenates deacylated LPE to a greater extent than LPC, while the reverse was true for leukocyte homogenates. Albumin inhibited deacylation of LPC and its conversion to PC by leukocytes, perhaps by binding the substrate (2 moles of LPC per mole of albumin). Other effects of albumin-stimulation of deacylation and acylation of LPE by macrophages, inhibition of deacylation and acylation of LPE by leukocytes-remain unexplained.