Evidence of decarboxylation of lysine by mammalian ornithine decarboxylase.

In enzymic preparations from mouse kidney stimulated with the anabolic steroid Durabolin (nandrolone phenpropionate) lysine and ornithine were shown to inhibit the decarboxylation of each other competitively. The Michaelis constants for the decarboxylations were approximately equal to the inhibition constants of the two amino acids. The pH optima of the decarboxylation of lysine and ornithine were found to be identical. Chromatographic studies of the enzyme preparation on a Sephadex G-150 Superfine column did not bring about a separation of the two enzyme activities. The ratio of the decarboxylating activities was practically the same during the elution. Lysine decarboxylating activity was also shown to be present in growth hormone stimulated rat liver. The results are in agreement with the assumption that the decarboxylation of lysine and ornithine is carried out by the same enzyme.