A BASIC PEROXIDASE ISOENZYME FROM VACUOLES AND CELL-WALLS OF VITIS-VINIFERA

The substrate profile of a basic peroxidase isoenzyme located in vacuo les and cell walls from Vitis vinifera and efficacy in oxidizing both vacuolar and cell wall phenolic substrate was studied. The reactivity of this isoenzyme with H2O2 [k(1)(CoI formation constant)=1.1 (quercet in), 1.6 (myricetin), 1.7 (trans-resveratrol) and 10.4 (coniferyl alco hol) mu M-1 sec(-1)] and with the phenolics [k(3) (CoII reduction cons tant)=20.7 (quercetin), 6.9 (myricetin), 11.9 (trans-resveratrol) and 8.7 (coniferyl alcohol) mu M-1 sec(-1)], suggests that the isoenzyme r eacts with H2O2 with a similar reactivity to that shown by other perox idases, and that both vacuolar and cell wall phenolics are excellent s ubstrates for CoII reduction. (C) 1997 Elsevier Science Ltd.