Partial purification and characterization of polyphenoloxidase from peppermint (Mentha piperita)
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2001
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Abstract
Polyphenoloxidase (PPO) of peppermint leaves ( Mentha piperita) was isolated by (NH4)2SO4 precipitation and dialysis. Its pH and temperature optima were 7.0 and 30°C, respectively. On heat-inactivation, half of the activity was lost after 6.5 and 1.5 min of treatment at 70 and 80°C, respectively. Sucrose, (NH4)2SO4, NaCl and KCl appeared to be protective agents of peppermint PPO against thermal denaturation. Km of this enzyme ranged from 6.25×10-3 M with catechol to 9.00×10-3 M with L-dopa. The I50 values of inhibitors studied on PPO were determined by means of activity percentage (I) diagrams. Values were 1.4×10-4 M, 1.7×10-4 M, 9.7×10-5 M, 2.45×10-4 M, 2.16×10-1 M, 1.83×10-5 M, 6.5×10-5 M, 1.4×10-2 M, 7.5×10-5 M, for potassium cyanide, glutathione, ascorbic acid, thiourea, sodium azide, sodium metabisulfite, dithioerythritol, β-mercaptoethanol and sodium diethyl dithiocarbamate respectively. Therefore, sodium metabisulfite was the most effective inhibitor. Copyright © 2001 Elsevier Science Ltd.
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Mentha x piperita , ascorbic acid , catechol oxidase , diethyldithiocarbamic acid , dithioerythritol , glutathione , mercaptoethanol , peppermint , potassium cyanide , sodium azide , sodium metabisulfite , stabilizing agent , thiourea , article , enzyme activity , enzyme analysis , enzyme purification , heating , in vitro study , phytochemistry , plant , storage