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Structural basis of noncanonical polyphenol oxidase activity in DLL-II: A lectin from Dolichos lablab.

Yashavanth, L. Vishweshwaraiah and Abhishek, Acharya and Balaji, Prakash (2018) Structural basis of noncanonical polyphenol oxidase activity in DLL-II: A lectin from Dolichos lablab. Biotechnology and Applied Biochemistry. pp. 701-717. ISSN 0885-4513

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Abstract

Lectins known to possess an additional enzymatic function are called leczymes. Previous studies reported a unique polyphenol oxidase (PPO) activity in DLL-II—a leczyme from Dolichos lablab. DLL-II shares a high sequence and structural homology with DBL—another leczyme from Dolichos biflorus. Incidentally, DBL possesses lipoxygenase activity, but not the PPO activity. Legume lectins usually possess two metal-binding sites A and B. Although these sites are conserved in both DBL and DLL-II, site A in DLL-II is occupied by Mn2+ and site B by Ca2+. In contrast, DLL-II binds Cu2+ and Ca2+ at sites A and B, respectively. Here, investigating the structural basis of PPO activity in DLL-II, we find that the PPO activity is only dependent on Cu2+, but not Ca2+; and the lectin activity requires only Ca2+. Further, our analysis suggests that an alternative mechanism of PPO reaction may be operative in DLL-II, which involves a mononuclear Cu2+ metal center; this is in contrast to the bi-nuclear Cu2+ metal center commonly observed in all PPOs. Importantly, structural and computational approaches employed here, we hypothesize possible PPO binding sites and the corresponding migration channels for accessing the active site.

Item Type: Article
Uncontrolled Keywords: leczyme, polyphenol oxidase, bi-functional lectins, tunnel computation, docking, substrate binding, metallozymes
Subjects: 600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
600 Technology > 08 Food technology > 22 Legumes-Pulses
Divisions: Molecular Nutrition
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 02 Jan 2019 10:32
Last Modified: 02 Jan 2019 10:32
URI: http://ir.cftri.com/id/eprint/13870

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