Carbohydrate and amino acid metabolism in Tuber borchii mycelium during glucose utilization:: a 13C NMR study

The metabolism of [1-C-13]glucose in the vegetative mycelium of the ectomycorrhizal ascomycete Tuber borchii was studied in order to characterize the biochemical pathways for the assimilation of glucose and amino acid biosynthesis. The pathways were characterized using nuclear magnetic resonance spectroscopy in conjunction with [1-C-13]glucose labeling. The enzymes of mannitol cycle and ammonium assimilation were also evaluated. The majority of the C-13 label was incorporated into mannitol and this polyol was formed via a direct route from absorbed glucose. Amino acid biosynthesis was also an important sink of assimilated carbon and C-11 was mainly incorporated into alanine and glutamate. From this intramolecular C-13 enrichment, it is concluded that pyruvate, arising from [1-C-13]glucose catabolism, was used by alanine aminotransferase, pyruvate dehydrogenase and pyruvate carboxylase before entering the Krebs cycle. The transfer of C-13-labeled mycelium on [C-12]glucose showed that mannitol, alanine, and glutamate carbon were used to synthesize glutamine and arginine that likely play a storage role. (C) 2003 Elsevier Science (USA). All rights reserved.