Nitrogen assimilating enzymes in the white button mushroom Agaricus bisporus
1994
Agaricus bisporus has the enzymic potential to assimilate ammonia by the activities of glutamine synthetase (EC 6.3.1.2), NAD-dependent glutamate dehydrogenase (EC 1.4.1.2) and NADP-dependent glutamate dehydrogenase (EC 1.4.1.4). It also contains glutamate synthase (EC 1.4.7.1) and a number of transaminating activities like glutamate-oxaloacetate transaminase (EC 2.6.1.1), glutamate-pyruvate transaminase (EC 2.6.1.2) and alanine-glyoxylate transaminase (EC 2.6.1.44). A. bisporus showed good growth in a defined buffered medium on glucose as a carbon source and a number of organic nitrogen compounds or ammonia as a nitrogen source. No growth was observed using nitrate as a nitrogen source. A. bisporus was not able to use organic nitrogen containing substances as a sole nitrogen and carbon source. Specific activities of the ammonia assimilating enzymes showed some variation when mycelia were cultivated on different nitrogen sources. Highest specific activities for glutamine synthetase, NAD-dependent glutamate dehydrogenase and NADP-dependent glutamate dehydrogenase were found when mycelia were grown on glutamate as a nitrogen source. Lowest values were found when the mycelia were grown on ammonia or glutamine. The specific activities of the ammonia assimilating enzymes showed no variation during maturation of the sporophores.
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