Enzymatic Characteristics of Two Forms of the Purified Glucoamylase from Rhizopus oryzae

Rhizopus oryzae로부터 정제한 두가지형의 Glucoamylase의 효소적(酵素的) 특성(特性)

These experiments were conducted to investigate general enzymatic characteristics of two forms(glucoamylase I and glucoamylase II) of the purified glucoamylase produced by Rhizopus oryzae. Molecular weights of glucoamylase I and glucoamylase II estimated by Sephadex G-100gel filtration, were approximately 101,000 and 115,000, respectively, and those estimated by SDS-polyacrylamide gel electrophoresis being 120,000 and 127,000, respectively. Isoelectric points of the above enzyme were pH 7.25 and pH 7.75. The optimum temperature was $50^{\circ}C$ and the enzyme was stable below $45^{\circ}C$. Optimum pH of both glucoamylase I and glucoamylase II was about pH 5.0. The stable pH range of them were pH 3.5-8.0 and 4.5-8.0, respectively. Michaelis constants of glucoamylase I and glucoamylase II toward souluble starch were 4.545 mg/ml and 5.560 mg/ml, respectively. $Hg^{++}$, $Pb^{++}$, p-CMB and IAA were inhibitors of glucoamylase I and $Hg^{++}$, $Mn^{++}$, p-CMB and IAA were inhibitors of glucoamylase II.

Rhiz. oryzae가 생산(生産) 정제효소(精製酵素) glucoamylase I (G I) 과 glucoamylase II (G II) 의 gel filtration에 의(依)하여 추정(推定)된 분자량(分子量)은 120,000, 127,000이었다. glucoamylase I 과 II 의 등전점(等電点)은 각각(各各) pH 7.25. pH 7.75 이었고 반응(反應) 최적온도(最適溫度)는 다같이 $50^{\circ}C$, 안정온도범위(安定溫度範圍) 는 다같이 pH5.0부근(附近)이었으며 안정(安定)pH범위(範圍)는 각각(各各) $pH3.5{\sim}8.0$, $pH4.5{\sim}8.0$이었다. 가용성전분(可溶性澱粉)에 대(對)한 Michaelis 상수는 glucoamylase I 이 4.545mg/ml, glucoamylase II 가 5.560mg/ml이었다. glucoamylase I 은 $Hg^{++}$, $Pb^{++}$, p-CMB, IAA에 의하여, glucoamylase II는 $Hg^{++}$, $Mn^{++}$, p-CMB, IAA에 의하여 저해(沮害)되었다.