Biochemical studies of enzyme-induced browning of African bush mango (Irvingia gabonensis) fruit pulp

• Published in: Preparative biochemistry & biotechnology 2022-08, Vol.52 (7), p.835-844
• Main Authors: Adeseko, Catherine Joke, Sanni, David Morakinyo, Lawal, Olusola Tosin
• Format: Article
• Language: English
• Subjects: Acidification; Calcium ions; Catechol; Copper; Deactivation; Enzymatic activity; Enzyme activity; Enzymes; Fruits; High temperature; Inactivation; Iron; Irvingia gabonensis; Levodopa; Magnesium; Mangoes; Molecular weight; pH effects; physicochemical properties; polyphenol oxidase; Pulp; purification; Tyrosine; Urea
• ISSN: 1082-6068; 1532-2297
• DOI: 10.1080/10826068.2021.1998113

The purpose of this study was to examine the biochemical properties of African bush mango (Irvingia gabonensis) pulp PPO. PPO was purified from I. gabonensis fruit pulp in three steps and characterized. A purification fold of 343 with specific activity of 216 U/mg and 13% recovery were obtained as well as molecular weight of 32.67 kDa was observed. The optimum pH and temperature were found to be pH 7.0 and 50 °C respectively while the enzyme showed instability at low pH 2-4 with total inactivation at pH 2 but maximal at pH 5-9 with remaining residual activity of 60-90%, whereas, total enzyme activity inactivation was observed at 90 °C. However, Cu 2+ , Fe 2+ and Mg 2+ enhanced the PPO activity but inhibited by Ca 2+ , Ba 2+ , K + and Na + . Notably, purified PPO was inactivated completely by urea at concentration above 10 mM while K m and V max values were estimated to be 7.34 mM and 0.36 U/min for catechol, 10.76 mM and 0.30 U/min for L- DOPA, and 14.90 mM and 0.26 U/min for tyrosine, respectively. The activity of PPO in I. gabonensis fruit and its juicy product could be controlled at high temperature in acidified medium.