CHARACTERIZATION OF 2 MAJOR CATIONIC PEROXIDASES FROM CELL-SUSPENSIONCULTURES OF VACCINIUM-MYRTILLUS

Two cationic peroxidases (VMPxC1 and VMPxC2) from cell suspension cult ures of Vaccinium myrtillus L. (Bilberry) were characterized. They sho w different amino acid compositions. Both enzymes are glycosylated, bu t VMPxC2 contains a higher percentage of carbohydrate. The molar absor ption coefficients at 403 mm were 101/mM per cm and 104/mM per cm for VMPxC1 and VMPxC2, respectively. The UV/visible absorption spectra of native enzymes and cyanide complexes, as well as the CD spectra were s imilar for the two enzymes and typical of plant peroxidases. However, differences were detected in the MCD spectra of the two enzymes which may be related to differences in the coordination of the heme iron. Bo th enzymes were able to oxidize coniferyl alcohol and ferulic, caffeic and p-coumaric acids in the pH range 3.4-7.6. VMPxC1 oxidizes all sub strates 5-6 times faster than VMPxC2, with the exception of p-CA. The rates of oxidation decreased in the order CAlc > FA > CA > p-CA for VM PxC1 and CAlc > FA > p-CA > CA for VMPxC2. The oxidation of FA, CA and p-CA has a pH optimum of 5.0 for VMPxC1, and pH 5.6 for VMPxC2. In th e case of coniferyl alcohol the pH optimum was 5.8 for both enzymes. T he work presented shows that these enzymes are products of two differe nt genes. Copyright (C) 1997 Elsevier Science Ireland Ltd.