Kinetics of soil urease inhibited by Hg

The relationship between the concentration of Hg and urease characteristic parameters in two meadow burozem and two phaeozem soils was investigated.Results show a close relationship between urease activity and organic matter content in the same type of soil.Hg inhibited soil urease activity obviously,and the relationship between HgCl2 and urease activities can be described by logarithmic equations significantly(P 0.05) or markedly significantly(P 0.01).It can be calculated that ecological dose(ED50) of HgCl2 based on the inhibition of urease activity was equal to 45.75、5.41、10.81 and12.41 mg kg-1 according to corresponding equations.The characteristic parameters of soil urease,including urease activity,Michaelis constant(Km),maximum reaction velocity(Vmax),and Vmax /Km decreased with the increase of Hg concentration,and the correlation was significant with few exceptions.To some extent,characteristic parameters of urease can be used as indexes to characterize the soil contamination of Hg.Hg behaves as a typical uncompetitive inhibitor to soil urease in this experiment.