PURIFICATION, CHARACTERIZATION AND KINETIC-PROPERTIES OF PEPPER FRUITACIDIC PEROXIDASE

A soluble acidic peroxidase (EC 1.11.1.7) was purified about 300-fold from the pericarp of pepper (Capsicum annuum L:) fruits by ammonium su lphate fractionation followed by chromatography in columns of Sephadex G-100, Q-Sepharose and Superose 12 PC 3.2/30. The purified enzyme has a pI of 3.8 and a M-r, determined by gel filtration, of 50 k. The enz yme was stable in a pH range from pH 6 to 9 and was resistant to high temperature. The ability of the acidic peroxidase to oxidize capsaicin was studied. The oxidation follows the accepted model for peroxidase oxidations, in which compound I (CoI) and compound II (CoII) appear to be the main intermediates in the catalytic cycle. Kinetic constants f or H2O2 [K-l (CoI formation constant) = 41 mu M-1 sec(-1)] and for cap saicin [K-3 (CoII reduction constant) = 3.5 mu M-1 Sec(-1)] suggest th at the acidic peroxidase has a higher H2O2 reactivity than other perox idases, and that capsaicin is a good substrate for CoII reduction. (C) 1997 Elsevier Science Ltd.