Characterization of two major cationic peroxidases from cell suspension cultures of Vaccinium myrtillus

Two cationic peroxidases (VMPxC1 and VMPxC2) from cell suspension cultures of Vaccinium myrtillus L. (Bilberry) were characterized. They show different amino acid compositions. Both enzymes are glycosylated, but VMPxC2 contains a higher percentage of carbohydrate. The molar absorption 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 similar 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. Both 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 substrates 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 VMPxC1 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 the case of coniferyl alcohol the pH optimum was 5.8 for both enzymes. The work presented shows that these enzymes are products of two different genes. Copyright (C) 1997 Elsevier Science Ireland Ltd.