Purification and Properties of Urease fromBrevibacterium ammoniagenes

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Abstract
Urease was purified to a homogeneous state from cell-free extracts of a strain of Brevibacterium ammoniagenes. The enzyme was found to have a molecular weight of 200,000, to consist of three identical subunits with a molecular weight of 67,000, and to have an isoelectric point at pH 4.1. The amino acid profile was similar to that of jack bean urease. Methionine and leucine were shown to be the N- and C-terminal residues, respectively. The enzyme contained 1 atom of nickel per subunit. The enzyme was most active at about pH 7 and at 65°C, and was stable betweeen pH 7 and 10 (at 30°C for 5 hr) and below 50°C (at pH 7.5 for l0min). Among the compounds examined, Hg2+, Cu2+, PCMB, and hydroxyurea inhibited the enzyme strongly. The Km value of enzyme for urea was found to vary from 18 to 72 mm depending on pH and the type of buffer used. It was proved that the enzyme can be used for the determination of urea by the reaction rate assay method.