Intermediary Metabolism of Phospholipids in Brain Tissue

Abstract

Abstract The conditions have been described for measuring quantitatively phosphocholine-glyceride transferase and choline phosphokinase activities in microgram quantities of nervous tissue. It was observed that the various parameters affecting enzyme activity in brain are quite similar to those previously reported for the liver enzyme. The enzymatic formation of labeled phosphatidylcholine from 14C-cytidine diphosphocholine was stimulated more than 20-fold on the addition of D-α,β-diglyceride to the incubation mixtures. Diglycerides having a high degree of unsaturated fatty acids were the most active substrates. The activity of phosphocholine-glyceride transferase was elevated in neonatal brain tissue (peak activity at 10 to 20 days postnatally). The enzyme activity was also elevated in a peripheral nerve undergoing demyelination. The neurone-rich grey structures of adult rabbit brain were 2- to 8-fold more active than adjacent white (myelinated) matter. Phosphocholine-glyceride transferase was predominantly located in the microsomal fraction of brain, but it is suggested that a significant portion of activity is also present in mitochondria.