THE MAGNESIUM-ION-DEPENDENT CLEAVAGE OF THE VINYL ETHER LINKAGE OF BRAIN ETHANOLAMINE PLASMALOGEN.

1. There was a significant decrease in the amount of endogenous ethanolamine phospholipids when preparations of whole brain were incubated in bicarbonate-Ringer solutions, leading in particular to the hydrolysis of vinyl ether groups. 2. The hydrolysis of ethanolamine phospholipids in such preparations was abolished in the absence of bivalent cations. 3. An enzyme present in extracts of acetone-dried brain powders that cleaved the vinyl ether linkage in ethanolamine plasmalogen maximally at pH 7.4 required Mg(2+) for activity. 4. The cleavage of the vinyl ether linkage of an ethanolamine lysoplasmalogen was enhanced in the presence of Mg(2+) but the requirement was not absolute.