Turnip (Brassica rapa) Peroxidase: Purification and Characterization

Partial purification of plant peroxidase from turnip ( Brassica rapa ) was optimized. Aqueous two phase system and precipitation by ammonium sulfate (as two parallel purification methods) were used. Polyethylene glycol/ammonium sulfate/NaCl (25:7:3%, w/v) system followed by gel-filtration chromatography gave a purification factor of about 36 fold. On the other hand, ammonium sulfate precipitation (60−80% deg) followed by gel filtration gave only about 13 purification fold. Hence, the aqueous two-phase system was more efficient and useful method as a primary purification step since it was less laborious, less time-consuming, and led to more purification factor. The partially purified turnip enzyme was stable at a pH range 2.6−6.0 and had an optimum pH at 4.0. The enzyme was stable up to 55 °C with an optimum activity at 35 °C.