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Studies on Bovine Rumen Bacterial Urease¹

Animal Research Institute, Agriculture Canada, Ottawa, Ontario, Canada, K1A 0C6

Abstract

The properties of rumen urease were studied. In the absence of high concentrations of dithiothreitol enzyme activity was rapidly lost; in its presence, the enzyme could be solubilized and purified in high yield. Maximum activity was observed between pH 7 and 8.5. The Km for urea with partially purified enzyme was .004 M with Vmax of 300 to 400 µmoles/mg/hr. No divalent metal ion requirement or activation by divalent metal ions could be demonstrated. Most divalent metal ions were inhibitory. The enzyme was inhibited by p-chloromercuribenzene sulfonate, N-ethylmaleimide and phosphate but not by ammonium ions. Apart from urea, hydroxyurea was also hydrolyzed by rumen urease. Hydroxyurea and phenylurea inhibited the hydrolysis of urea. The inhibition by hydroxyurea could be reversed by increasing the urea concentration. Rumen urease was inhibited by a variety of hydroxamates. Acrylamide gel electrophoresis indicated that only one type of urease is found in the rumen, having a much lower molecular weight than jack-bean urease.

¹ Contribution No. 584 from the Animal Research Institute.

² The authors acknowledge the technical assistance of Mr. L. R. Beaton.