Physical and Chemical Properties of an Extracellular Low-Molecular-Weight Substance from the Brown-Rot Basidiomycete Fomitopsis palustris

抄録

A low-molecular-weight, extracellular substance with one-electron-oxidizing activity was isolated from wood-degrading cultures of the brown-rot basidiomycetous fungus Fomitopsis palustris. The substance was partially purified by acetone precipitation, gel-filtration chromatography on Sephadex G-50 and G-25, and DEAE-Sepharose ion-exchange chromatography. The partially-purified material was a glycopeptide composed of (54%, w/w) protein and (42%, w/w) neutral carbohydrate, containing (0.06%, w/w) Fe (II) by weight. The molecular weight as estimated by Tricine-SDS-PAGE was 7, 200-10, 000; whereas the molecular weight as determined by size-exclusion or gel-filtration chromatography was 1, 000-5, 000. The glycopeptide reduced O₂to H₂O₂ and Fe (III) to Fe (II), and thus could generate hydroxyl radical via a Fenton reaction. One mg of the partially-purified glycopeptide reduced 1.7μ mol of Fe (III) to Fe (II) and contained at least 0.6μ mol of α-hydroxyketone or endiol groups. Most of the α-hydroxyketone groups were 1-amino-2-ketoses produced by the condensation of side-chain amino groups and carbohydrate aldehydes. The function of the glycopeptide in brown-rot decay is discussed.