Biochemical properties of phosphatase in the leaves of wheat

The biochemical kinetics of phosphatase was studied with spectrophotometer.The experiment results showed that in the dydrolysis of pNPP by phosphatase,K_m was 6.554 mmol/L and V_(max) was 0.774×10~3 U/(mg protein).The optimal pH of this enzyme was 6.8 and the optimal temperature was 45℃ in the ten-minute thermal preservation,but the time for the enzyme to lose 50% of its activities was 12 minutes in the thermal preservation at 50 ℃,3.75 minutes in the thermal preservation at 60℃,and 1.8 minutes in the thermal preservation at 70℃.Different metallic ions and complexing agents affected the activity of the enzyme to some extent,Mg~(2+) and Ca~(2+) were capable of activating the enzyme,and Zn~(2+),Cu~(2+) and Mn~(2+) showed an inhibitory effect on the activity of the enzyme.EDTA,sodium dihydrogen phosphate and ammonium metavanadate also presented an inhibitory effect on the activity of the enzyme.These inhibitions could be divided by Lineweaver-Burk plot into non-competitive and competitive and other types whose inhibition constants were 5.87 mmol/L,2.47 mmol/L and 8.2 mmol/L,respectively.