Effect of pyridoxine deficiency on activities and amounts of aspartate aminotransferase isozymes in rat tissues.

The enzyme and antigen activities of aspartate aminotransferase [EC 2.6.1.1] isozymes in several tissues of rats fed on pyridoxine-deficient or control diet for 4 weeks were determined. The enzyme activities in liver (supernate, mitochondria), heart (supernate), brain (mitochondria), and muscle (mitochondria) preparations of the deficient rats were abnormally low, whereas those in other tissue preparations were similar to those of control rats. In liver and heart preparations, the antigen activities of the deficient rats were similar to those in controls, but in brain and muscle mitochondria they were abnormally low. These findings suggest that the activity and the amount of this enzyme are regulated in different ways in different tissues, and suggest that the coenzyme level affects metabolic regulation of the enzyme molecule.