THE ANAEROBIC FUNGUS PIROMYCES SP STRAIN E2 - NITROGEN REQUIREMENT AND ENZYMES INVOLVED IN PRIMARY NITROGEN-METABOLISM

The anaerobic fungus Piromyces sp. strain E2 appeared restricted in ni trogen utilization. Growth was only supported by ammonium as source of nitrogen. Glutamine also resulted in growth, but this was due to rele ase of ammonia rather than to uptake and utilization of the amino acid . The fungus was not able to grow on other amino acids, albumin, urea, allantoin, or nitrate. Assimilation of ammonium is very likely to be mediated by NADP-linked glutamate dehydrogenase (NADP-GDH) and glutami ne synthetase (GS). One transaminating activity, glutamate-oxaloacetat e transaminase (GOT), was demonstrated. Glutamate synthase (GOGAT), NA D-dependent glutamate dehydrogenase (NAD-GDH), and the transaminating activity glutamate-pyruvate transaminase (GPT) were not detected in ce ll-free extracts of Piromyces sp. strain E2. Specific enzyme activitie s of both NADP-GDH and GS increased four- to sixfold under nitrogen-li miting conditions.