Scission of polysaccharides by peroxidase-generated hydroxyl radicals.
Cell-wall polysaccharides can be broken down non-enzymatically in vitro by scission of backbone bonds in a Fenton reaction system producing hydroxyl radicals (OH*) (Fry, S.C. (1998). Biochemical Journal, 332, 507-515). OH* can also be generated enzymatically from O2 by horseradish peroxidase (HRP) in a complex reaction cycle involving NADH or dihydroxyfumarate (DHF) as reducing substrate (Chen, S.-X., & Schopfer, P. (1999). European Journal of Biochemistry, 260, 726-735). Based on these recent findings the possibility that HRP can be used to degrade cell-wall polysaccharides in vitro was investigated. The production of OH* from O2 by HRP in the presence of NADH or DHF was confirmed by EPR spectroscopy using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap. Chemical scission of polysaccharides (dextran, pectin, xyloglucan) by HRP-generated OH* was demonstrated using a viscometric assay. The reaction could be inhibited by an array of OH* scavengers, confirming the involvement OH* as the causative agent for macromolecule cleavage. The significance of these findings for the biochemical function of peroxidase in cell-wall loosening processes underlying cell expansion and related physiological processes is discussed.
Schweikert
C
C
Albert-Ludwigs-Universität Freiburg, Institut für Biologie II, Germany.
Liszkay
A
A
Schopfer
P
P
D002473:Cell Wall / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D017665:Hydroxyl Radical / Q000737:chemistry*; D009195:Peroxidase / Q000737:chemistry*; D010944:Plants / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*
D011134:Polysaccharides; D017665:Hydroxyl Radical; D009195:Peroxidase