α-Amylase(E.C.3.2.1.1. 2-1. 4-glucan 4-glucanohydrolase) from $\underline{Bacillus}$ $\underline{subtilis}$, which is an extracellular endoenzyme and hydrolyzes α-1, 4-glucosidic linkage of polysaccharides (Starch) was partially purified about nine times of the crude enzyme by the starch-adsorption column chromatography and generally characterized, and the optimum condition for enzyme protein synthesis in the culture media was studied.
This enzyme contents in the media showed enhancement through the induction by starch which is a natural substrate, and it seemed to need calcium(Ⅱ) and iron(Ⅲ) ion in maintaining its activity and to require the proper ratio of carbon and nitrogen sources(about 3:1 respectively) for good enzyme protein synthesis.
The optimum adsorption of this enzyme to starch was carried out at 30℃ and after 30 min-stirring, and 40% of enzyme activity was recovered by the starch-column chromatography. On the viewpoint of application of this enzyme, the anion-exchange chromatography can hard be recommended because of the poor yield and purification index. Its specific activity after purification was 24 u mole/min/mg protein.
The pH and temperature optima 5.5 6.5 and 45˚ 55℃ respectively, and calcium(Ⅱ) was seemed to be essential for activity while EDTA inhibited the enzyme activity seriously.
$\underline{Bacillus}$ $\underline{subtilis}$의 α-amylase 는 아밀로오즈나 아밀로펙틴의 α-1,4-glucoside 의 결합을 가수분해하는 효소로서 배지에 포도당이 존재하면 효소 생성이 억제되는 억제 효소이다. 효소의 생성을 위하여 $Ca^{++}$ 이온과 $Fe^{+++}$ 이온을 필요로 하며 탄소원 (soluble starch)과 질소원 $((NH_4)_2HPO_4)$의 비가 3:1 일때 가장 좋은 효소 활성도를 나타낸다.
$\underline{Bacillus}$ $\underline{subtilis}$ culture broth 로 부터 균체를 제거한 조효소 용액을 얻고 이것을 전분 흡착 크로마토그라피옙 의해서 9배 가량 정제하고 다시 DEAE-Cellulose 이온교환 크로마토그라피를 통해서 3배 정도 더 정제시켰다. 조 효소 용액의 전분 흡착은 0℃ 에서 30분동안 하였다. 위 두 과정을 통해서 얻은 효소의 전분(soluble starch) 에 대한 비활성도는 24 u mole/min/mg protein 이었으며, km 값은 $5.13\times10^{-3} g/ml$ 였다.
이 효소의 최적 pH 와 최적온도는 각각 5.5 - 6.5, 그리고 45℃ - 55℃ 였다.
효소의 활성을 위해서는 Ca(Ⅱ) 이 꼭 필요하며, 이 효소는 EDTA 에 의해서 강하게 저해를 받는다.
