Purification of an Infection-Related, Extracellular Peroxidase from Barley

Increases in two extracellular peroxidases were observed following inoculation of barley (Hordeum vulgare L.) with the powdery mildew pathogen (Erysiphe graminis DC.: Fr. f. sp. hordei Em. Marchal). The more prominent isozyme, P8.5, was purified from intercellular wash fluids by acetone precipitation, ion-exchange chromatography, isoelectric focusing, and gel filtration. Purified P8.5 is a heme-containing, glycoprotein with a M(r) of 35,000. It has eight cysteine residues. A highly specific, high-titer antiserum to deglycosylated P8.5 was produced.