Study on catalytic kinetics of commercial pectinase from Aspergillus niger

The characteristics in catalytic kinetics of commercial pectinase from Aspergillus niger were determineded.The results showed that the optimum pH and optimum temperature of the enzyme for the hydrolysis of pectin(enzyme substrate)were pH 3.8 and 50 ℃,respectively.The behavior of the enzyme during hydrolysis of pectin followed Michaelis-Menten kinetics,with K_(m)=5.16±0.13 mg·mL~(-1)and V_(max)=2.73±0.02 μg·mL~(-1)·min~(-1),at pH 3.8 and 50 ℃.The stability of the enzyme was investigated,and the results showed that the enzyme was stable in a pH range from 3.4 to 4.2 and at temperatures50 ℃.The effects of metal ions on the enzyme were also studied.Na~(+) and K~(+)had no influence on enzyme activity.Ca~(2+) in the concentration of 0.1 mmol/L increase activity of the enzyme,while Mg~(2+),Mn~(2+),Co~(2+),Ni~(2+),Hg~(2+),Ag~(+),Zn~(2+),Cu~(2+) and Fe~(3+) showed various degrees of inhibitory effects on the enzyme in the concentration of 5.0 mmol/L,among which Zn~(2+) in the concentration of 5.0 mmol/L inhibited activity of the enzyme by 17.4 %,and Cu~(2+) by 88.9 %,Fe~(3+) by 100 %.