Purification and biochemical characterization of polyphenol oxidase of African bush mango (Irvingia gabonensis) fruit peel

Abstract Polyphenol oxidase (PPO) is a browning causative agent in fruits and vegetables and thereby lowers their economic and market values. The main objective of this study was to extract, purify and investigate physicochemical properties of PPO from peel of African bush mango (Irvingia gabonensis). The crude extract obtained from the peel of Irvingia gabonensis using PPO-extracting buffer was subjected to the three-step purification and thereafter the biochemical properties of the purified PPO were determined. A purification fold of 685 and specific activity of 411 U/mg were achieved with 20 % recovery while molecular weight was 53.22 kDa. The enzyme was optimum at pH 7.0 and 50 °C while thermal and pH inactivation was observed at 80 and 90 °C and pH 2 after 1 and 6 h incubation respectively. Notably, enzyme inhibition was observed in the presence of urea, ascorbic acid, Ca2+, Na+, and K+ while Km of 14.34, 17.84 and 20.32 mM and Vmax of 0.46, 0.42 and 0.39 U/min were observed for catechol, l -DOPA and l -tyrosine respectively. Subjecting African bush mango to conditions that inhibit the PPO activity of its peel will prolong its shelf-life and improve its usability in food processing and technology.