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Purification and characterization of a polyphenol oxidase from the seeds of field bean (Dolichos lablab).

Paul, B. and Gowda, L. R. (2000) Purification and characterization of a polyphenol oxidase from the seeds of field bean (Dolichos lablab). Journal of agricultural and food chemistry, 48 (9). pp. 3839-3846. ISSN 0021-8561

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The polyphenol oxidase from field bean (Dolichos lablab) seeds has been purified to apparent homogeneity by a combination of ammonium sulfate precipitation, DEAE-Sephacel chromatography, phenyl agarose chromatography, and Sephadex G-200 gel filtration. The purified enzyme has a molecular weight of 120 +/- 3 kDa and is a tetramer of 30 +/- 1.5 kDa. Native polyacrylamide gel electrophoresis of the purified enzyme revealed the presence of a single isoform with an observed pH optimum of 4.0. 4-Methyl catechol is the best substrate, followed by catechol, and L-3,4-dihydroxyphenylalanine, all of which exhibited a phenomenon of inhibition by excess substrate. No activity was detected toward chlorogenic acid, catechin, caffeic acid, gallic acid, and monophenols. Tropolone, both a substrate analogue and metal chelator, proved to be the most effective competitive inhibitor with an apparent K(i) of 5.8 x 10(-)(7) M. Ascorbic acid, metabisulfite, and cysteine were also competitive inhibitors.

Item Type: Article
Uncontrolled Keywords: Polyphenol oxidase; field bean seed; Dolichos lablab; catecholase; tetramer; substrate inhibition; tropolone
Subjects: 600 Technology > 08 Food technology > 22 Legumes-Pulses
500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 16 Enzyme Chemistry
Divisions: Protein Chemistry and Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 05 Jan 2009 09:37
Last Modified: 18 Nov 2016 10:48
URI: http://ir.cftri.com/id/eprint/2152

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