Polysaccharide degradation by Fenton reaction- or peroxidase-generated hydroxyl radicals in isolated plant cell walls

Abstract

The formation of hydroxyl radicals (OH ) by peroxidase was confirmed by EPR spectroscopy using ethanol/α-(4-pyridyl-1-oxide)- N-tert-butylnitrone as a spin-trapping system specific of OH . The effect of OH , generated either non-enzymatically with the Fenton reaction (H 2O 2+Fe 2+) or with horseradish peroxidase in the presence of O 2 and NADH, on cell walls isolated from maize ( Zea mays) coleoptiles or soybean ( Glycine max) hypocotyls was investigated. OH produced by these reactions attack polysaccharides in the wall, demonstrated by the release of a heterogeneous mixture of polymeric breakdown products into the incubation medium. The peroxidase-catalyzed degradation of cell-wall polysaccharides can be inhibited by KCN and superoxide radical (O 2 − ) or OH scavengers. These data support the hypothesis that OH , produced by cell-wall peroxidases in vivo, act as wall-loosening agents in plant extension growth.