Partial purification and characterisation of banana [Musa (AAA Group) ‘Gros Michel’] polyphenol oxidase

Abstract

SummaryPolyphenol oxidase (PPO) from pulp of banana [Musa (AAA Group) ‘Gros Michel’] was extracted and precipitated with 80% saturated ammonium sulphate followed by conventional column chromatography on Sephacryl S‐200 HR and fast protein liquid chromatography on Mono Q column. The lyophilised PPO obtained from Sephacryl S‐200 HR column was used for characterisation and inhibition studies. The partially purified PPO obtained from the Mono Q column exhibited at least three isoenzymes. The banana PPO had optimum pH for activity at 7 and it was stable around the same pH. Only 48% of initial enzyme activity was lost after heating at 70 °C for 30 min. The enzyme was completely inhibited by 2 mm sodium metabisulphite, 2 mm l‐cysteine, 4 mm ascorbic acid, and 100 mm 4‐hexylresorcinol. The Km and Vmax of banana PPO for dopamine were 2.08 mm and 0.124 mm min−1 respectively.