ON THE SITE OF ACTION OF PHOSPHATIDE ACYL‐HYDROLASE ACTIVITY OF RAT BRAIN HOMOGENATES ON LECITHIN

Abstract

— ‐The hydrolysis of 2‐ [¹⁴C]acyl‐labelled and [Me‐³H]choline‐labelled lecithins by rat brain homogenates has been studied. The acyl‐labelled substrate was hydrolysed with the production of both radioactive lysolecithin and radioactive free fatty acid in the proportions of 60 per cent and 40 per cent; traces of labelled mono‐ and diglyceride were also formed. In addition to radioactive lysolecithin the [³H]choline‐labelled lecithin also gave rise to much smaller amounts of radioactive water soluble derivatives, consisting almost entirely of free choline and phosphorylcholine with only traces of glycerylphosphorylcholine. The results provide evidence for the production of a mixture of 1‐ and 2‐acyl isomers of lysolecithin by phospholipase action in brain homogenates at pH 7·4, the latter predominating slightly.