Carbohydrate metabolism in Agaricus bisporus (Lange) Imbach: metabolism of [14C] labelled sugars by sporophores and mycelium

When growing sporophores and vegetative mycelium of Agaricus bisporus had been supplied with [14C] labelled hexoses for varying periods of time, the major compounds labelled in both forms were mannitol, trehalose, glutamate, alanine and an unidentified substance. Mannitol was strongly labelled after application of [14C] fructose but only weakly when [14C] glucose was applied. The relative rates of oxidation by sporophores of labelled mannitol, trehalose, glucose and fructose were assessed by measuring 14CO2 production. Glucose and trehalose were the most rapidly oxidized substrates. Glucosephosphatase isomerase (E.C. 5.3.1.9) was extracted from sporohores and assayed. The conversion of glucose-6-phosphate to fructose-6-phosphate by the enzyme was competitively inhibited in vitro by 6-phosphogluconate. The control of mannitol synthesis and the functions of mannitol and trehalose are discussed. (author)