A physiological role of the glyoxylate and TCA cycles in fruitbody formation of the coppertolerant brown-rot fungus Fomitopsis palustris
Jeong-Jun Yoon, T Hattori, M Shimada
Changes in activity of the representative enzymes involved in biosynthesis of oxalic acid (oxalate) and carbon metabolism of glucose were investigated in relation to the fruit body formation of the copper-tolerant brown-rot fungus Fomitopsis palustris. Changes in specific activities of the two glyoxylate (GLOX) cycle key enzymes (isocitrate lyase (ICL) and malate synthase (MS)), the two oxalate-forming enzymes (oxaloacetase (OXA) and glyoxylate dehydrogenase (GLOXDH)), and a tricarboxylic acid (TCA) cycle enzyme (isocitrate dehydrogenase (IDH)), were measured during the fungal growth. The enzymes for GLOX cycle and oxalate synthesis in mycelia showed greater activities at the stage of mycelial growth than at the fruiting stage. At the fruiting stage, the IDH/ICL activity ratios was reversed, rising from 0.3 to 2.0. Thus, the results obtained indicate that IDH of the TCA cycle plays a more important role than ICL of GLOX cycle for the fruit body formation of F. palustris, whereas ICL is more important than IDH for the oxalate biosynthesis at the earlier satge of the cultivation.