The Activity of Glycerophosphocholine Phosphodiesterase in Brain Tissue

Abstract

Considerable interest has been generated in recent years about the supply of choline (Ch) for acetylcholine (ACh) synthesis in the brain (for short review see reference 4). This interest commenced with observations made over a decade ago that the capacity of brain tissue to synthesize Ch was non-existent, though this conclusion may have to be modified in view of more recent findings (23). Thus the brain has to assimilate Ch from the blood. There are some doubts whether the free Ch in the blood is the most immediate source of Ch for ACh synthesis and interest has therefore focussed on two problems. Is the Ch brought to the brain in a lipid-bound form and releases some Ch or is the lipid bound form assimilated into the pool of brain lipid -bound Ch from which Ch is released? The fact that there is in brain tissue a Ch-generating system (11,12,18), suggests that there is a mechanism for releasing Ch from Ch lipids in brain tissue which is enzymic in nature. The possible mechanisms have been discussed recently by Ansell and Spanner (4).