ORNITHINE-KETOACID AMINOTRANSFERASE IN HUMAN LIVER WITH REFERENCE TO PATIENTS WITH HYPERORNITHINAEMIA AND FAMILIAL PROTEIN INTOLERANCE

The results of studies in which intravenous ornithine loadings were administered to normal subjects suggested a rate-limiting function of ornithine-ketoacid aminotransferase (OKT) in the conversion of ornithine to glutamate. The liver OKT activity exhibited a specific pattern during human development, with high values before birth. No change was observable in the apparent Km of OKT for l-ornithine and 2-oxoglutarate during development. Two patients with hyperornithinaemia had a specific activity of liver OKT which was considerably lower than expected for the age, but with normal apparent substrate constants, whereas the liver ornithine transcarbamylase activity was found to be normal. Furthermore, a patient with familial protein intolerance had a somewhat depressed activity of liver OKT. The rate of amino nitrogen disappearance after ornithine infusion was also subnormal in two patients with protein intolerance. © 1969.