Reduced phosphorylcholine hydrolysis by homogenates of temporal regions of Alzheimer's brain.

The hydrolysis of p-nitrophenylphosphorylcholine, p-nitrophenylphosphate, and phosphorylcholine was quantitated in homogenates prepared from the occipital and temporal regions of control and Alzheimer's Disease patient brain. There were no significant differences detected in activities of enzymes cleaving the first 2 compounds. A 78% reduction in the capacity for hydrolyzing phosphorylcholine by temporal homogenates from Alzheimer's patients compared to controls was demonstrated. The hydrolysis of this substrate by occipital homogenates was identical to control values. These results may explain the lack of cognitive improvement of Alzheimer's patients receiving dietary supplements of either choline or lecithin.