Cerebrocortical plasma membrane serine base exchange enzyme activity in hypoxia

Phosphatidylserine (PtdSer) is involved in signal transduction and in apoptosis. Peculiarities of its metabolism (1) are relevant for this study. N2 treatment stimulates the incorporation of [14C]serine (Ser) into PtdSer of cerebrocortical slices and in cerebrocortical plasma membranes (PM) serine base exchange enzyme (SBEE) activity is lowered by G protein activator. PtdSer radioactivity of PM from slices incubated with [14C]Ser was greater in hypoxia than in controls. SBEE activity of PM from slices, incubated in a similar manner and assayed at pH 8.2 and pH 7.4 based on a preliminary study, was lower in hypoxia. The hypoxia induced incorporation of [14C]Ser into slice PtdSer was due to stimulation of the SBEE isoform that exchanges Ser and ethanolamine and that in brain membrane is activated by fatty acids. We suggest the presence of different SBEE isoforms in PM differently influenced by hypoxia.