20458

The Banana Pulp Polyphenol Oxidase is a Tyrosinase

Saeid Nematpour Faternh نويسنده , Haghbeen Kamahldin نويسنده , Khalili Babaei Masoumeh نويسنده , Rastgar Jazii Ferdows نويسنده , Nouraeen Omidreza نويسنده , Baharloui Yancheshmeh Maedeh نويسنده

526

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8

The best extraction result for the polyphenol oxidase (PPO) from the Musa cavendishii pulp was obtained using a phosphate buffer (0.02 M, pH 7) containing PVP (2%), triton X-I 00 (1 O~) and ascorbic acid (0.01 %). Two active PPO isozymes were obtained applying a procedure involving dialysis, stepwise precipitation, DEAE and Sephadex column chromatography. The most active isozyme cresolase and catecholase activities in the presence of 4-[(4-Methylphenyl)azo]-phenol and caffeic acid showed an 11.67 and 13.3 fold recovery, respectively, after isolation. It exhibited a single band PAGE and had a MW of 58.2 kD and pI of 5.28 with the kinetic parameters of(Km = 18.6 JlM and Vmax = 2.8 muM min-I) for caffeic acid and (Km = 0.94 mM and Vmax = 14.8 muM min^-I) for dopamine. The presence of dopamine in banana pulp and peel was established and the results were discussed in terms of the identity and physiological role of the banana PPO in a collective and conclusive manner.

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