Properties of ornithine aminotransferase from rat liver, kidney and small intestine

Abstract

1. 1. A method for purification and crystallization of ornithine aminotransferase ( l-ornithine:2-oxoacid aminotransferase, EC 2.6.1.13) from rat kidney is described. 2. 2. Various properties of the enzymes from liver, kidney and small intestine were similar, including their ultracentrifugal and electrophoretic behavior, absorption spectra, pH optima, K m values for ornithine and α-ketoglutarate, K m value for pyridoxal phosphate and specificities for amino acceptors from ornithine. 3. 3. The precipitation lines of the three enzymes against the antisera of kidney and liver ornithine amino transferase all fused with each other on Ouchterlony double diffusion plates. 4. 4. From these results, the ornithine transaminase enzymes of liver, kidney and small intestine seem to be the same protein. 5. 5. Only the activity of the liver enzyme was elevated in vivo by high protein diets. Injection of estradiol elevated only the activity of the kidney enzyme, and this was due to increase in ornithine aminotransferase protein estimated by immuno-analysis. The difference in the activities of kidney ornithine aminotransferase in male and female rats was due to the different contents of ornithine aminotransferase protein in their kidneys. The activity of ornithine aminotransferase in the small intestine did not change on these treatments.