ISSN:
1432-072X
Keywords:
Wood decay
;
White-rot fungi
;
Lignin biodegradation
;
Fungus physiology
;
Repression by glutamate
;
Glutamate dehydrogenase
;
Glutamine synthetase
;
Intracellular amino acids
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Previous research showed that addition of nutrient nitrogen to ligninolytic (stationary, nitrogen-starved) cultures of the wood-decomposing basidiomycete Phanerochaete chrysosporium causes a suppression of lignin degradation. The present study examined early effects on nitrogen metabolism that followed addition of NH 4 + and l-glutamate at concentrations that yield similar patterns of suppression. Both nitrogenous compounds were rapidly assimilated (〉80% in 6 h). Both caused an initial 80% or greater increase in the intracellular glutamate pool and had similar effects in increasing the specific activities of NADP- and NAD-glutamate dehydrogenases and glutamine synthetase. Differences between the effects of added NH 4 + and glutamate showed that suppression was not correlated with intracellular pools of arginine or glutamine, nor was the maintenance of an elevated glutamate pool required to maintain the suppressed state. While a portion of the initial glutamate suppression could be attributed to an effect on central carbon metabolism through glutamate catabolism by NAD-glutamate dehydrogenase, the long term suppression by glutamate and the suppression by NH 4 + were more specific. Suppression by NH 4 + or glutamate in the presence or absence of protein synthesis (cycloheximide) followed essentially identical kinetics during 12 h. These results indicate that nitrogen additions cause a biochemical repression of enzymes associated with lignin degradation. Results are consistent with the hypothesis that nitrogen metabolism via glutamate plays a role in initiation of repression.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00527074
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