Studies on Acylase Activity and Microorganisms. XXIV. Properties of δ-Ornithine Acylase : 5-N-Acylornithine Amidohydrolase.

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In order to study the enzymatic properties of the δ-ornithine acylase in KT 801 (Pseudomonas sp.), experiments were carried out with the purified enzyme preparation. This enzyme has a pH optimum around 8.2 toward 5-N-benzoyl-L-ornithine. It is inhibited by Co²⁺, Zn²⁺, Fe³⁺, Cu²⁺, Hg²⁺, EDTA, and o-phenanthroline. The inactivation for EDTA is reversed by addition of Ca²⁺ or Mn²⁺ after dialysis. Km value toward 5-N-benzoyl-L-ornithine was calculated to be 1.8×10^-4M. As a results of the investigation of substrate specificity, it was found that this enzyme hydrolyses not only L form of 5-N-benzoylornithine, but D form in the rate of about one sixth. The ratio of the activities toward L and D form remained constant all through the purification steps. These result strongly suggest that one enzyme has the both activities. Also, susceptible substrate to δ-ornithine acylase require absolutely the presence of a free carboxyl group, the presence of a free α-amino group is desirable for ready susceptibility of the substrate, but it is not an absolute requirement, and the susceptibility are considerably affected by carbon chain length between the carboxyamide group and the free carboxyl group. This enzyme shows no α-amino acylase activity. On the other hand, δ-ornithine acylase is quantitatively released when EDTA-lysozyme spheroplasts are made. From these result, it has been proposed that δ-ornithine acylase of KT 801 is at the cell surface.