Abstract: The invention relates to a method and a composition for the enzymic determination of aspartame in aqueous solutions. The method is carried out such that the sample solution is incubated essentially in the presence of oxo-glutarate, glutamate-oxaloacetate transaminase (GOT), malate dehydrogenase (MDH), NADH and a protease, and the decrease in the NADH extinction is measured photometrically.

Abstract: The invention relates to NAD(P)H-dependent nitrate reductase from yeasts, to a process for the preparation thereof and to the use thereof in a reagent for determining nitrate. The nitrate reductase is characterized by a molecular weight of about 350 000 D and can be obtained by yeast cells which have been cultivated in a completely synthetic nutrient medium with nitrate as the sole nitrogen source and which contain nitrate reductase being disrupted in phosphate buffer, the crude extract being chromatographed on an anion exchanger, the fractions containing nitrate reductase being mixed with protein, concentrated by ultrafiltration and dried by fluidized bed granulation. The reagent for determining nitrate contains, besides the nitrate reductase prepared in this way, also NAD(P)H and a color reagent for determining nitrite.