생쥐 뇌의 세포질 분획에서 $H^3$-phosphatidylinositol ($H^3$-PI)을 기질로하여 phosphatidylinositol-specific phospholipase C (PI-PLase C) 효소 활성도를 보았을 때, 50mM Tris-maleate buffer, pH 5.5인 산성에서 최고의 활성도를 나타냈고, pH 5.5와 pH7.2에서 시간별 활성도를 비교하여 보았을 때 pH 5.5에서는 10분 까지 직선적인 활성도증가를 보였으나 그 이후는 거의 완만한 증가를 나타내는 반면, pH 7.2에서는 50분 까지도 지속척언 활성도 증가를 나타내는 양상을 보였다. 이 효소는 $0^{circ}C$에서 활성도가 매우 낮았고, $37^{circ}C-40^{circ}C$ 사이에서 가장 높은 활성도를 보였으며, 그 이상의 온도에서는 급격한 활성도의 감소를 나타냈다. 본 실험의 반응조건하에서 $10;{mu}l$ ($3.14;{mu}g;protein/{mu}l$)의 효소량이 가장 높은 활성도를 보였으며 효소 단백질의 증가에 따라서 활성도는 오히려 약간의 감소를 나타냈다. 이 효소는 pH 5.5와 pH 7.2에서 여러 cation들의 영향을 보았을 때, 특히 $Ca^{2+}$에 의해서 각각 3.0배와 4.2배의 현저한 활성화 효과를 나타냈으며, $Hg^{2+}$와 $Ag^+$에 의해서는 $10;{mu}M$ 농도에서도 심한 저해효과를 나타냈는데, 중성 pH보다 산성 pH에서 더 현저한 저해효과를 나타냈다.
When the cytosolic phosphatidylinositol-specific phospholipase C (PI-PLase C) activity from mouse brain was estimated by using $H^3$-labelled phosphatidylinositol ($H^3$-PI) as a substrate, it showed the maximum enzyme activity at pH 5.5 with 50 mM Tris-maleate buffer solution. The enzyme activity was increased very sharply at pH 5.5 within 10 min. incubation and slow down after that. But at physiological pH 7.2, the activity was increased continuously until 50 minutes. This enzyme was very sensitive to the reaction temperature and showed a low activity at $0^{circ}C$ and the maximum hydrolysis occurred at $37^{circ}C-40^{circ}C$ When the enzyme activity estimated in the presence of various amounts of enzyme, the maximum activity showed at the addition of $10;{mu}l$ ($3.14;{mu}g;protein/{mu}l$) of enzyme into $200;{mu}l$ of reaction volume. In the effects of different kinds of cations, the enzyme was stimulated significantly in the presence of 1 mM calcium ion at the rate of 3.0 times and 4.2 times at pH 5.5. and pH 7.2, respectively. On the contrary, the enzyme activity was inhibited seriously even in the low concentration of $10;{mu}M$ mercury and silver ions at both pH.
