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. Oil 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 degrees C with an optimum activity at 35 degrees C.