%0 Journal Article %A M. Morales %A J. Alcántara %A A. Ros Barceló %T Oxidation of trans-Resveratrol by a Hypodermal Peroxidase Isoenzyme from Gamay rouge Grape (Vitis vinifera) Berries %D 1997 %R 10.5344/ajev.1997.48.1.33 %J American Journal of Enology and Viticulture %P 33-38 %V 48 %N 1 %X The ability of the hypodermal grapevine peroxidase isoenzyme B5 to oxidize trans-resveratrol was studied. The results showed that the oxidation of trans-resveratrol by this isoenzyme was strictly dependent on H2O2 and follows the accepted model for peroxidase oxidations, in which compound I (Col) and compound II (Coll) appear to be the main intermediates in the catalytic cycle. The reactivity of grapevine peroxidase isoenzyme B5 with H2O2 [k1 (Col formation constant) = 1.73 µM-1 s-1] and with trans-resveratrol [k3 (Coll reduction constant) = 11.9 µM-1 s-1], suggests that the isoenzyme reacts with H2O2 with a similar reactivity to that shown by other peroxidases, and that trans-resveratrol is an excellent substrate for Coll reduction. Further, the strong oxidizing activity of this basic peroxidase isoenzyme at pH 3.0 to 4.0 suggests that the peroxidase-mediated reaction is well adapted to the acidic medium of the vacuole, in which grapevine peroxidase B5 is mainly located. These results reveal the special kinetic characteristics of the grapevine peroxidase isoenzyme B5 to oxidize trans-resveratrol, and enable us to assign a specific metabolic function to this grapevine isoenzyme which acts as a constitutive (non-inducible) marker of disease resistance in grapevine leaves and shoots. %U https://www.ajevonline.org/content/ajev/48/1/33.full.pdf