Purification and Characterization of Acid Urease fromLactobacillus reuteri

Acid urease was purified from Lactobacillus reuteri and characterized. The enzyme preparation was electrophoretically homogeneous and the molecular weight of the enzyme was estimated to be 220,000. The enzyme consisted of three kinds of polypeptides, designated as α, ß and γ, with molecular weights of 68,000, 16,100 and 8,800, respectively, in a (α1β2γ1)2 structure. The isoelectric point of the enzyme was 4.7. The nickel content was found to be 1.8 atoms of nickel per α1β2γ1 unit. The amino acid profile was different from those of known bacterial neutral ureases. The enzyme was most active at pH 2 and at around 65°C. It was stable between pH 3 and 8, and below 50°C. The Km for urea was 2.8 mM at pH 2. The enzyme activity was inhibited by Ag+, Hg2+, Cu2+, p-chloromercuribenzoate and acetohydroxamate. The acid urease eliminated urea in alcoholic beverages that are acidic in general.