The [formula omitted] phosphatase activity of ubiquitin from bovine erythrocytes

Abstract

1.1. Ubiquitin, a unique protein with esterase and carbonic anhydrase activity, has been found to have also a p-nitrophenyl phosphatase activity.2.2. This phosphomonoesterase activity of ubiquitin has an acidic pH optimum; its true substrate appears to be the phosphomonoanion, with a Km of 1.8 × 10−3M.3.3. It is competitively inhibited by the typical acid phosphatase inhibitors, arsenate (Ki = 1.3 × 10−3M), molybdate (Ki = 1.2 × 10−6M), and phosphate (Ki = 1.4 × 10−3M).4.4. These inhibitors have no effect on the CO2 hydration and p-nitrophenyl acetate esterase activities of the ubiquitin.5.5. Acetazolamide slightly inhibited the p-nitrophenyl phosphatase activity.