PURPOSE:To obtain the titled enzyme useful for a diagnostic enzyme for the quantitative determination of ammonia in a biospecimen, economically on an industrial scale, by culturing a fungal strain belonging to Coprinus genus and capable of producing glutamic acid dehydrogenase and separating the enzyme from the culture product. CONSTITUTION:A fungal strain belonging to Coprinus genus and capable of producing glutamic acid dehydrogenase (e.g. Coprinus macrorhizus f. microsporus, IFO 7662) is inoculated in a medium and cultured at 25 deg.C for 5 days under shaking to obtain a seed culture liquid. The liquid is inoculated in a jar fermenter containing a medium and cultured at 25 deg.C for 3 days under aeration at a rate of 7.5l/min and agitation at 250rpm. After cultivation, the culture product is filtered to separate wet microbial cells, which are disintegrated, extracted with potassium phosphate buffer solution, etc., and centrifuged. The objective enzyme can be obtained by concentrating the supernatant liquid and purifying the concentrate by gel-filtration.
