Urease from the lugworm, Arenicola cristata.

Abstract

Urease from animal tissues is often considered to be of microbial rather than animal origin. A determination of key properties of urease isolated from an animal tissue should permit an assessment of the origin of the enzyme. Lugworm (A. cristata) gut urease was purified seventy fold from tissue homogenates by chromatography on DEAE-cellulose and Sephadex G-150. The apparent molecular weight by gel-filtration was 200,000. The Km for urea declined from about 3.5 mM at pH 6 to 0.38 mM at pH 7 then decreased with increasing pH to 0.2 mM at pH 9 in Tris-phosphate buffer. The Vmax was constant between pH 6 and 8 then declined above pH 8. N-ethylmaleimide, AgNO3 but not iodoacetamide inhibited enzyme activity. Acetohydroxamate, hydroxyurea, and hydroxylamine inhibited in the manner similar to the inhibition seen with ureases from other sources. The characteristic properties of A. cristata gut urease—low Km, pattern of variation of Km with pH, molecular weight, and sensitivity to inhibitors—distinguish this urease from urease in bacteria, plants, land snails and cestodes.