E. Rahiala, M. Kekomäki, J. Jänne
Feb 10, 1971
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Biochimica et biophysica acta
Abstract
Abstract The effect of l -canaline, a structural analogue of l -ornithine, was studied on several mammalian enzymes in vitro. The results obtained with three ornithine metabolizing enzymes indicated that canaline is not an effective competitor of ornithine in these reactions. However, canaline strongly inhibited the activity of all seven pyridoxal-dependent enzymes studied, including amino acid decarboxylases [ornithine decarboxylase (EC 4.1.1.17), 5-hydroxytryptophan decarboxylase (EC 4.1.1.28)], aminotransferases [ornithine-ketoacid aminotransferase (EC 2.6.1.13), tyrosine aminotransferase (EC 2.6.1.5)], ornithine transcarbamylase (EC 2.1.3.3) and plasma diamino-oxidase (EC 4.1.3.6). The reversibility of this inhibition by excess pyridoxal phosphate, as well as a strong interaction between canaline and pyridoxal phosphate in aqueous solution, support the view that canaline inhibition is due to complex formation between canaline and the pyridoxal coenzyme. l -canaline is one of the most potent inhibitors of pyridoxal enzymes. Ornithine-ketoacid amino-transferase, for example, was inhibited by 50% in the presence of 3 ° 10 −6 M l -canaline.