The hydrolysis of the alkenyl group from enthanolamine-plasmalogen by oligodendroglial cell-enriched fractions

Abstract

The rate of hydrolysis of the 1-0-alkenyl group of sn-1-alk-1?-enyl-2-acyl-glycerylphosphorylethanolamine (alkenyl, acyl-GPE; ethanolamine plasmalogen) by plasmalogenase is higher in oligodendroglial cell-enriched fractions from bovine brain compared with fractions enriched in neuronal perikarya and astroglia. The distribution of plasmalogenase activity in membrane fractions isolated from bovine oligodendroglia has been compared with that of 'marker' enzymes. The highest specific activity was in a fraction enriched in plasma membranes, whilst most activity was recovered in an endoplasmic reticulum membrane fraction. In bovine oligodendroglial cell homogenates, the enzyme had a neutral pH optimum, had no requirement for divalent cations and its activity towards 1-alkenyl-GPE (lysoplasmalogen) was half that with alkenyl, acyl-GPE. C(16) alkenyl groups were hydrolysed more rapidly than C(18) alkenyl groups. With (3)H-labelled alkenyl, acyl-GPE as substrate, radioactivity in released aldehydes appeared in fatty acids esterified in phospholipid while the oxidation of fatty aldehydes was blocked by the addition of NADH. An NAD-dependent aldehyde dehydrogenase was found to be present in oligodendroglia which exhibited highest activity towards C(14)?C(18) aldehydes (K(m), 2 ?M).