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Utilization of Carbohydrates by Rhynchosporium secalis II. Absorption and Metabolism of Glucose, Galactose and Galacturonic acid
Author(s) -
AYRES P. G.,
OLUTIOLA P. O.
Publication year - 1973
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1973.tb03095.x
Subject(s) - galactose , mannitol , mycelium , carbohydrate , biochemistry , carbohydrate metabolism , trehalose , chemistry , fungus , metabolism , biology , botany
Glucose, galactose and galacturonic acid were taken up at different rates by the fungus Rhynchosporium secalis and were intracellularly converted to other forms of carbohydrate at different rates. These differences explain why, when there is only a single source of nutrient carbon in the growth medium, development of the fungus is greatest when glucose is present and least when galactose is present. Glucose and galactose were taken up by the same mechanism for their uptake showed a reciprocal competitive inhibition. Uptake mechanisms had a high affinity for glucose (apparent K m 2.76 m M ) and galacturonic acid (apparent K m 3.10 m M ) and a low affinity for galactose (apparent K m 29.67 m M ). After uptake, galactose accumulated in the mycelium, whereas glucose and galacturonic acid were rapidly converted to other soluble carbohydrates, principally trehalose and mannitol. The insoluble carbohydrates within the mycelium were little affected by the type of carbohydrate that was supplied to the fungus.