Effect of treatment with pyridoxine on aspartate aminotransferase activities in pyridoxine-deficient rat tissues.

In rat liver, 90% of the aspartate aminotransferase is present as the holoenzyme. In pyridoxine deficiency, the ratio of holoenzyme activity to total activity is markedly reduced, but after pyridoxine injection it was found to rapidly increase, although the total enzyme activity remained low for a few days. The activities of aspartate aminotransferase isozymes in pyridoxine-deficient rat tissues and the effect of pyridoxine treatment on their activities were examined. The intestinal enzyme activities of pyridoxine-deficient rats were readily reconstituted in the presence of pyridoxal phosphate in vitro, but the enzyme activities in liver and muscle in the deficient rats required several days for complete recovery, suggesting that active enzyme was synthesized de novo in these tissues.