Galactose, aspartate crossway and rhythm inhibition in Aspergillus niger [endogenous rhythm, transaminases]
1980
Jerebzoff, S. | Jerebzoff-Quintin, S. (Toulouse-3 Univ., 31 (France). Lab. de Phytohormones)
When the glucose/K('+) balance in the medium is favourable to rhythm expression in Aspergillus niger Van Tieghem, galactose has an inhibitory effect on amplitude but not on period length of the rhythm. Galactose is active when its level reaches 1/10 of that of glucose. On liquid media a small quantity of glucose is neccessary to start growth on galactose. Under these conditions U('14)C-galactose is rather slowly metabolized. After 6 h of feeding on the labelled galactose medium, this sugar is converted into glucose, which is used both for the synthesis of compounds derived from C(,3) and C(,4) units and for synthesis of polysaccharides and perhaps small peptides. The labelling of the macromolecules always remains low. The insoluble carbohydrates of the mycelium are little affected by the type of sugar supplied to the fungus. The metabolism on galactose differs from the metabolism on glucose mainly in a decrease of the free asparagine pool and a simultaneous equivalent increase of the free aspartate pool: such an effect could not be correlated with an increase of the aspartate aminotransferase activity. Supply of aspartate but not of glutamate into the agar medium inhibits the rhythm amplitude. So, the damping effect of galactose on the rhythm might be at least partly due to its effect on the regulation of the aspartate crossway
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