Endogenous polyamine content of the ectomycorrhizal fungus Paxillus involutus, as well as the activity of its
biosynthetic enzymes in relation to mycelia ageing were investigated in this work. Polyamines in free, PCA-soluble
and insoluble conjugated forms, are present in Paxillus involutus mycelia in relatively high amounts and the ratio
of putrescine to spermidine is age-dependent. Both arginine- and ornithine-decarboxylases are present, but
putrescine biosynthesis proceeds mostly via ornithine decarboxylase and decreases with the age of mycelia. There
was a large release of free polyamines from mycelia which showed age-dependent features. Clear polyamine uptake
was observed in 2-wk-old mycelia and no competition between putrescine and cadaverine was detected. Putrescine
uptake seems to reduce ornithine decarboxylase activity, but does not affect arginine decarboxylase.