Reactivation of the apoenzyme of aspartate aminotransferase in serum.

Apoenzyme of aspartate aminotransferase in serum can be reactivated conveniently by addition of 100 mumoles/l pyridoxal phosphate to the reaction mixture, without extending the usual minimum pre-incubation period in the operation of the LKB 8600 reaction rate analyzer. Normal sera contain some apoenzyme, the amount of which, as well as that of holoenzyme, is greatly increased by damage to skeletal muscle. This may be due to direct injury or to the indirect effects of anoxia; e.g., following surgery with extracorporeal circulation. Myocardial infarction also increases the levels of both apo- and holoenzymes, but changes in the two levels follow similar time courses and apo- and holo-aminotransferases disappear from the circulation at similar rates.