Enzymes involved in ammonia assimilation in the fungus Acremonium persicinum

Abstract

SUMMARYAcremonium persicinum grown in batch culture with ammonium tartrate as the nitrogen source possessed an NADP+-dependent glutamate dehydrogenase and a glutamine synthetase. Glutamate synthase was not detected under the culture conditions used. Kinetic studies of the NADP÷-dependent glutamate dehydrogenase at 25°C and pH 7.6 revealed an apparent K m of 3.2 x 10 -4 M for 2-oxoglutarate and an apparent K m of 1.0 × 10 -s M for ammonium ions, with corresponding apparent Vma s values of 0.089 and 0.13 /~mol substrate converted/min/mg of protein, respectively. Glutamine synthetase was measured by the 7-glutamyl transferase reaction at 30°C and pH 7.55. This transferase reaction of glutamine synthetase had a higher rate at 30°C than at 25°C or 37°C.

Intermediary Metabolism

“…The relative importance of the different pathways of ammonia fixation has been estimated in N. crassa and A. nidulans and might vary between fungi and in different developmental stages or culture conditions (Hummelt and Mora, 1980;Kusnan et aI., 1989;Wilcock et al, 1992).…”