Isolierung und eigenschaften einer cyanamid-hydratase (E.C.-Gruppe 4. 2.1.) aus Myrothecium verrucaria Alb. u. Schw.

Abstract

Initially the growth of Myrothecium verrucaria was found to be inhibited through cyanamide. A concentration of 10-4 M of cyanamide caused a slight inhibition. The addition of cyanamide to the culture medium brought about an induction of a cyanamide hydratase. This enabled the fungi to grow, with cyanamide as the only source of nitrogen. Urea was formed first, and then decomposed into ammonia and carbon dioxide. Cyanamide hydratase was isolated from the fungi mycelium and concentrated approximately seventy times. The characteristics of cyanamide hydratase were examined, i. e., to show that the reaction NH = C = NH + H2O → (NH2)2CO could be proved quantitatively, and that there was an absence of inhibitors in the preparations. In addition, it was found that the temperature optimum ranged between 40–55° C, that the pH optimum was pH 7.7 and that the Km of the reaction was 3,7 · 10-6 Mol/l. The cyanamide hydratase seemed to be crucial for the reaction. The velocity of the reaction was greatly enhanced through additional Mn2+. The enzyme was classified as one of the E. C. group 4.2.1. The question of an active secretion of the enzyme into the culture medium was discussed. Cyanamid beeinflußt das Wachstum des Bodenpilzes Myrothecium verrucaria. Aus Mycelien in Reinkultur wird eine spezifisch wirkende Cyanamid-Hydratase isoliert, angereichert und charakterisiert. Dieses Enzym ist durch das Substrat induzierbar. Das Cyanamid reagiert in molekularem Verhältnis zu Harnstoff. Dabei liegt der optimale Wirkungsbereich bei 40–55° C und einem pH-Wert von 7,7. Mn2+ fördert die Umsetzungsgeschwindigkeit. Die Michaelis-Konstante wird mit 3,7 · 10-6 Mol/l bestimmt. Das Enzym ist auch im Nährmedium nachzuweisen. Die Frage einer aktiven Exkretion wird diskutiert.