황산암모늄 분획 (35-60%) 효소액을 사용하여 Aspergillus fumigatus IFO 5840의 cytidine deaminase에 대한 효소학적 성질을 조사하였다. 효소반응의 전처리시간은 25분이었으며 본 효소의 최적pH와 최적온도는 각각 6.8-7.2와 $37^{circ}C$부근이었다. PH에 대한 안정성은 pH7.2에서 9.0의 범위에서 안정하였으며 온도의 안정성은 4$0^{circ}C$에서 10분 열처리시 대체로 안정하였으나 6$0^{circ}C$에서 20분간 처리시는 77%의 효소실활을 나타내었고 7$0^{circ}C$에서 25분간 처리하였을때 완전히 실활되었다. 본 효소의 활성화 에너지 값(Ea)은 14.190kca1/mo1이었고 온도계수 ($Q_{10}$ )는 2.163이었다.
Cytidine deaminase (EC 3.5.4.5) from Aspergillus fumigatus IFO 5840, which was the first cytidine deaminase to be found in a mold, was fractionated with ammonium sulfate (35-60%). When the enzyme solution in 0.25M of Tris-HCI buffer (pH 7.2) was preincubated at $37^{circ}C$ for 25min, the enzyme activity was reached to maximum state. The optimum pH and temperature for the enzyme activity were found to be 6.8 to 7.2 and near $37^{circ}C$, respectively. The enzyme was stable in a pH 7.2 to 9.0, and was generally stable at 4$0^{circ}C$, but after treating at 6$0^{circ}C$ for 20min at the optimal pH, 17% of the enzyme activity was inactivated, and disappeared completely by treating at 1$0^{circ}C$ for 25min. Activation energy (Ea) of fungal cytidine deaminase was calculated as 14.190 Kcal /mol by the Arrhenius plot, and temperate coeffient ($Q_{10}$ ) of the enzyme was calculated as 2.163.
