Biosynthesis of N-acetyl-L-aspartic acid in vivo and in brain homogenates

Abstract

The content of N-acetyl-L-aspartic acid in urine from pancreatectomized dogs and alloxan-diabetic rats was measured. Urinary N-acetyl-L-aspartic acid was extracted by ethyl acetate and hydrolyzed, and the aspartic acid was determined by colorimetry. The results show that in alloxan-treated rats, N-acetyl-L-aspartic acid is present in relatively high concentration in urine, while it is completely absent in the controls. In pancreatectomized dogs, the excretion of N-acetyl-L-aspartic acid in urine is much higher than in normal dogs. Furthermore, when the citric acid cycle is inhibited by the addition of fluoroacetic acid to brain homogenates, there is accumulation of radioactive N-acetyl-L-aspartic acid in the medium whereas none could be detected in controls. It is concluded that the formation of N-acetyl-L-aspartic acid in the brain can alleviate the accumulation of an excess of acetate. It is suggested that N-acetyl-L-aspartic acid may serve as a carrier of the acetyl group.