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Abstract Polyphenol oxidase catalyzes oxidative conversion of polyphenols to their respective quinones. These have been exploited in various biotechnological processes. The kinetics and molecular docking interaction of turmeric PPO on some inhibitors are here described. The enzyme was purified using aqueous two-phase partitioning. The subunit and the native molecular masses of the purified turmeric PPO were 69 ± 2.0 kDa and 66.8 ± 3.5 kDa respectively, suggesting its monomeric nature. The Km and Vmax of the C. longa PPO for pyrogallol were 5.8 ± 0.6 mM and 722.9 ± 17.0 units/mg protein respectively leading to turnover number (kcat) and first order rate constant (kcat/Km) of 831.6 ± 5.0 s-1 and 1.43 × 105 s-1 M-1 respectively. The purified enzyme was activated at the lowest concentration in KCl and CuSO4, whereas was fairly stable in the presence of NaCl, ZnSO4 and NH4Cl. The inhibition constant (Ki) obtained from Dixon plot for ascorbic acid, β-mercaptoethanol, citric acid, cysteine, EDTA, glutathione and kojic acid were 7.8, 1.7, 5.5, 2.0, 8.1, 3.3 and 6.4 mM respectively. In-depth analyses, revealed that cysteine was the most potent of all the inhibitors investigated. The binding interaction of the purified enzyme with inhibitors revealed that EDTA, Kojic acid and Cysteine have 2 hydrogen bonds formed while citric acid, ascorbic acid and glutathione had 4, 5 and 3 respectively. In conclusion, the kinetics and inhibition studies of the purified turmeric PPO could be deployed in the control of browning and several industrial and biotechnological applications.
Ilesanmi et al. (Mon,) studied this question.