A comparison of ornithine aminotransferase from human and rat sources

Ornithine aminotransferase was purified from human liver, rat liver and rat kidney. Sodium dodecyl sulphate polyacrylamide gel electrophoresis indicated a subunit molecular weight of 45,000 in all three cases. Estimations of the native molecular weights of ornithine aminotransferase were determined by Sephadex G-200 chromatography in the presence and absence of 0.1% (w/v) Triton X-100. Human and rat enzymes were tetrameric in the presence of detergent but the rat subunits aggregated further in its absence. Characterisation of ornithine aminotransferase from the two rat sources indicated that they were the same protein. The human and rat enzymes were similar but not identical.