The occurrence of N‐acetylaspartate amidohydrolase (Aminoacylase II) in the developing rat1

Of The amino acids and derivatives, N‐acetyl‐L‐aspartic acid is present in a uniquely high level (5–6 μmol/g) in the brain of mammals after myelination has occurred. Much lower levels (0·06–0·17 μmol/g) are found prior to this stage of brain development (Tallan, 1957). In non‐nervous tissues, on the other hand, only trace amounts of this acetyl amino acid are present (Tallan, Moore and Stein, 1956). N‐acetyl aspartic acid serves as an excellent source of acetyl groups for lipogenesis in the developing rat brain (D'Adamo and Yatsu, 1966; Dadamo, Gidez and Yatsu, 1968). Non‐nervous tissues such as kidney and mammary gland also rapidly metabolize the acetyl amino acid, the former tissue converting the acetyl group primarily to CO2 and the latter to fatty acids (Benuck and D'Adamo, 1968). An enzyme with a high specificity for N‐acetyl‐L‐aspartic acid initially termed aminoacylase II, was originally isolated from hog kidney by Birnbaumet al. (1952). Since the physiological role of the substrate is not known, it was of interest to study the occurrence of this enzyme, N‐acetyl‐L‐aspartate amidohydrolase (EC 3.5.1.15), in developing tissues of the rat.