Kintic properties of peroxidase from leaves of Brassica napus L. Var. Okapi

Peroxidases (Ec 1.11.1.7) are hemoproteins which are widely used in diagnostic test kits as well as various experimental tests. For this reason, there is a great need to suitable isozymes from differrent plant sources.Turnip (Brassica napus L.) is an annual herb cultivated mainly for its valuable seed oil. It is closely related to horseradish (the only source of commercial peroxidase, HRP), thus it may be an alternative HRP. In this research, plant material (leaves no.5, 6, 7) were collected and extracted at the rosset stage. Enzyme assay and kinetic studies were performed at 25˚C and λ=470 nm. The result showed that the maximum activity of the enzyme was at 50˚C and pH=6. During 30 min, the enzyme was stable at 25-55˚C and pH= 4.5-7.5 with no reduction in its activity, but it was inactive at 60-70˚C. The addition of 0.3-0.6 mM various salts including (Na+, K+,Ni2+, Co2+, Ca2+, Ba2+ and Zn2+) revealed that the persence of K+, Na+ and Zn2+ increased the activity of the enzyme while Co2+ and Ni2+ had an inhibition effect. The comparison of different concentrations of NaCN and NaN3 on the enzyme activity showed NaCN is more stronger inhibitor of peroxidase in Brassica napus. In the presence of 0.002 mM NaCN, the enzyme activity reduced to half compared with control.