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

Istituto di Chimica Biologica "Giorgio Fornaini," Università degli Studi di Urbino, Via A Saffi, 2, 61029 (PU), Urbino, Italy.
Fungal Genetics and Biology (Impact Factor: 2.59). 08/2003; 39(2):168-75. DOI: 10.1016/S1087-1845(03)00006-9
Source: PubMed

ABSTRACT The metabolism of [1-13C]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 [1-13C]glucose labeling. The enzymes of mannitol cycle and ammonium assimilation were also evaluated. The majority of the 13C 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 13C was mainly incorporated into alanine and glutamate. From this intramolecular 13C enrichment, it is concluded that pyruvate, arising from [1-13C]glucose catabolism, was used by alanine aminotransferase, pyruvate dehydrogenase and pyruvate carboxylase before entering the Krebs cycle. The transfer of 13C-labeled mycelium on [12C]glucose showed that mannitol, alanine, and glutamate carbon were used to synthesize glutamine and arginine that likely play a storage role.

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    • "In general, the presence of mannitol in the medium greatly increased the rate of PSA; this trend was especially pronounced for C. flaccumfaciens. The central role of mannitol metabolism in the growth of the truffle mycelium is well established (Ceccaroli et al. 2003). Although neither of the fungal storage sugars mannitol nor trehalose was actively exuded by the ectomycorrhizal fungus Cantharellus cibarius, 13C NMR analyses suggested that both sugars were released into the culture medium (Rangel-Castro et al. 2002). "
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    Fungal Ecology 12/2013; 6(6):527-538. DOI:10.1016/j.funeco.2013.05.006 · 2.93 Impact Factor
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    • "Firstly, fungal mannitol may be involved in the sequestration of carbohydrates from host. Since many plants are unable to metabolize mannitol, the conversion of plant hexoses into mannitol seems an ideal strategy for the fungal pathogen or mutualist, providing a means for fungi to store carbohydrates and reducing power in a form not accessible to the host (Ceccaroli et al., 2003; Dulermo et al., 2009). As in planta mannitol accumulation mainly occurred when conidiophores emerged, the latter authors suggest that this polyol could be necessary for spore survival or germination. "
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    Frontiers in Plant Science 05/2013; 4:131. DOI:10.3389/fpls.2013.00131 · 3.95 Impact Factor
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    • "No sequence coding for mannitol 1-phosphatase was identified when the only mannitol 1-phosphatase, cloned and functionally characterized from Eimeria tenella (GenBank AAC38954), was used as BLAST query against the T. melanosporum genome. As the enzymatic activity of mannitol 1-phosphatase has been detected previously in T. borchii mycelial cell-free extracts (Ceccaroli et al., 2003), the enzymatic activities of all the enzymes involved in mannitol metabolism was performed in mycelia and fruiting bodies of T. melanosporum. As shown in Fig. 3(a1), all enzymatic activities, including mannitol 1-phosphatase, were detected and, among them, the specific activity of mannitol dehydrogenase was significantly higher in mycelia than in fruiting bodies. "
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