The Enzymatic Synthesis of N-Acetyl-L-aspartic Acid by Subcellular Preparations of Rat Brain

The acetyl coenzyme A-l-aspartate N-acetyltransferase activity of a previously reported preparation obtained from the supernatant phase of rat brain homogenates by ammonium sulfate fractionation was reinvestigated and substantiated. The enzyme activity was located in particles, probably microsomes, dispersed in the supernatant fluid. A homogenate system with comparatively high N-acetylaspartate synthesizing capacity in the presence of acetyl-CoA and l-aspartate is described. The activity of this preparation was recovered in association with the particulate structures. Acetone-dried powders of the crude mitochondrial fraction and a microsomal fraction had specific activities approximating 40 and 20% that of the respective fresh tissue constituents.