Studies on Bovine Rumen Bacterial Urease 1

The propert ies 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 #moles/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 b y 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. (