Observations on the Regulation of Glutamate Dehydrogenase Activity inCoprinus lagopus

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Abstract
Extracts of the mycelium of Coprinus lagopus (sensu Buller) contain two glutamate dehydro-genases with different optimum pH values. One is assayed with nicotinamide adenine dinucleotide (NAD-GDH) and the other with nicotinamide adenine dinucleotide phosphate (NADP-GDH). Changes in specific activity of the enzymes were investigated during the growth of both a monokaryon (H9) and a dikaryon (H9 x TC) in different media and after the transfer of mycelium from one growth medium into another. In the latter case the magnitude of the changes in enzyme activity could be altered by modification of either the carbon or the nitrogen source in the transfer medium. It is concluded from the results obtained that neither glutamate nor the ammonium ion seems to regulate directly the synthesis of either enzyme. However, some of the results are in accordance with the view that a product of glucose metabolism represses the synthesis of the NAD-GDH and derepresses or induces that of the NADP-CDH and evidence that this regulator is 2-oxoglutarate was obtained. It is also concluded that the complete system of regulation must involve more than one molecule.

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