A new peroxidase from the roots of the Algerian white turnip (Brassica rapa, variety rapa): extraction, purification, characterisation, and antioxidant potential

摘要

Due to its various biological activities, the roots of Brassica rapa (turnip), has been applied as a therapeutic agent in traditional medicine. The current study aimed to purify a plant peroxidase (POD; designated as TRP) from Algerian white turnip (B. rapa, variety rapa) roots, to homogeneity and to characterise it biochemically. The molecular weight of the purified TRP was determined to be similar to 58 kDa as estimated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and high-performance liquid chromatography (HPLC). The TRP Reinheitzahl values (RZ) and specific activity were 2.9 and 14,500 U/mg, respectively. Its N-terminal sequence exhibited high identity with those of class III-PODs. TRP showed optimal activity at 55 degrees C and pH 6 (guaiacol), was completely inhibited by sodium azide (NaN3) and potassium cyanide (KCN) and exhibited greater catalytic efficiency than that of the well-known horseradish peroxidase (HRP) from Armoracia rusticana. TRP demonstrated antioxidant activities with 45 and 61.49 of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(center dot)) and hydroxyl ((OH)-O-center dot) radical scavenging, respectively, as well as ferrous ion chelating (52.96) and reducing (48.32) powers. This study provides information regarding the potential role of TRP in enzyme therapy (as applied in the pharmaceutical and medicinal industries), with biological eradication of free radicals.