New role for glyoxylate cycle enzymes in wood-rotting basidiomycetes in relation to biosynthesis of oxalic acid

Abstract

The key enzymes of the glyoxylate cycle, isocitrate lyase (ICL) and malate synthase (MS), were detected in varying amounts in the mycelia of the woodrotting basidiomycetes tested, although they were grown in a glucose-rich medium. The highest specific activities of ICL (0.37 U/mg protein) and MS (0.63 U/mg protein) were measured for the brown-rot basidiomycetes Laetiporus sulphureus and Fomitopsis palustris, respectively. The results indicate that the glyoxylate cycle enzymes occur in wood-rotting basidiomycetes as the seemingly "constitutive" enzymes at varying levels. The glyoxylate cycle enzymes, including malate dehydrogenase (MDH), and the oxalate-producing enzymes glyoxylate dehydrogenase (GDH) and oxaloacetase (OXA) were found to have good correlation with biosynthesis of oxalic acid and fungal growth, which was also confirmed by use of an ICL inhibitor. A new role for the glyoxylate cycle is discussed in relation to oxalic acid biosynthesis in wood-rotting basidiomycetes.