Protection effect of boric acid and β-mercaptho ethanol against H2O2 inactivation of Urease

Urease (urea amidohydrolase, EC 3.5.1.5) catalyzes the hydrolysis of urea to produce ammonia and CO2. Kinetics studies have been performed using UV-vis spectrophotometer at 40oC and pHs 5.5, 7.2, 8. Result showed that urease inhibition by hydrogen peroxide is a kinetics pH-dependent, such that inhibition is maximal on the condition of pH value 8 while the inhibitory effect hydrogen peroxide at pH 5.5 was minimum. The kinetic parameters Km and Vmax enzyme obtained from Lineweaver–Burk plot in absence of hydrogen peroxide was 4.52mM and 1.03mM.min-1 respectively .In presence of H2O2, increasing pH leads to decrease Vmax and km. The results showed that in pH 8, boric acid and βmercaptho ethanol protected urease against hydrogen peroxide. Protectable of β-mercaptho ethanol is more than of boric acid. Such, the results demonstrates that 30 mM boric acid and βmercaptho ethanol afforded to protect 80% and 90% of urease activity from the loss as compared to the respective control samples.