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


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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Available from: Roberta Saltarelli, Apr 15, 2014
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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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    • "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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