Apoenzyme of aspartate aminotransferase in serum in health and disease.

Aspartate aminotransferase activity has been measured in the sera of normal subjects and in patients with various diseases both with and without addition of pyridoxal phosphate to the assay medium. Considerable quantities of apoaminotransferase were present in almost all samples. In normal subjects this potentially-active enzyme corresponds on average to about half the holoenzyme present before reactivation with pyridoxal phosphate. However, considerable variations between individuals were found in the amounts of apoaminotransferase present in serum, and also between groups of patients with various diseases.