Regulation of the choline, ethanolamine and serine base exchange enzyme activities of rat brain microsomes by phosphorylation and dephosphorylation.

The base exchange enzyme activities of rat brain microsomes were estimated subsequent to preincubations under conditions for either protein phosphorylation or dephosphorylation. Quantitatively the choline base exchange activity was most affected by these treatments. Exposure of the microsomes to alkaline phosphatase resulted in a decrease of all three base exchange activities. Pretreatment with a cAMP-dependent protein kinase resulted in increases of all 3 enzyme activities. Conditions favoring protein kinase C phosphorylation resulted in stimulation of the choline base exchange activity.