Effects of Metal-ions on Enzyme Activities from Hansenula anomala B-7 Grown in Medium Containing Cadmium

카드뮴 함유 배지에서 배양된 Hansenula anomala B-7의 Malate Dehydrogenase 활성에 미치는 금속 이온의 영향

This study was carried out to investigate the effect of cadmium ion on activities of cadmium-adapted malate dehydrogenase (adapted-MDH), which is defined to be an enzyme obtained from an extreme cadmium-tolerant yeast Hansenula anomaul B-7 grown in medium containing 1 mM cadmium ion. Cadmium-nonadapted malate dehydrogenase (nonadapted-MDH), which is defined to be enzyme expressed in the cells grown in $Cd^{2+}$ -free medium was also characterized by the same manner. Activities of the adapted-MDH and the nonadapted-MDH were strongly induced to 450% and to 150% in comparision with the control examined with 1 mM $Cd^{2+}$, respectively. The adapted-MDH activity was stimulated to 147%, 150%, and 135% compared with the control analyzed with 1 mM $Zn^{2+}$, 1 mM $Mn^{2+}$, and 1 mM $Ca^{2+}$, respectively and to 925%, and 250% compared with the control analyzed in the presence of 2 mM $Cd^{2+}$, and 2.5 mM $Zn^{2+}$, respectively. Km values of the adapted-MDH and the nonadapted-MDH were calculated to be the same 6.9 mM for L-malate, respectively. The Km value of the nonadapted-MDH was not changed by $Cd^{2+}$ while Vmax of the nonadapted-MDH was increased by $Cd^{2+}$. In contrast, both the Km and the Vmax values of the adapted-MDH were changed by $Cd^{2+}$.

카드뮴 1 mM를 함유한 배지에서 배양된 고도 카드뮴 내성 효모 Hansenula anomala B-7으로부터 분리한 malate dehydrogenase(카드뮴 적응 MDH)와 카드뮴을 함유하지 않은 배지에서 배양된 사용균주의 malate dehydrogenase(카드뮴 비적응 MDH)활성에 미치는 금속 이온의 영향을 비교 검토했다. 카드뮴 적응 MDH와 비적응 MDH 활성은 1 mM $Cd^{2+}$에 의하여 대조구에 비하여 450%와 150%가 각각 증가되었으며, 카드뮴 적응 MDH 활성은 1 mM $Zn^{2+}$, $Mn^{2+}$과 $Cu^{2+}$에 의하여 각각 147%, 150%와 135% 증가되었다. 더욱이, 카드뮴 적응 MDH 활성은 2 mM $Cd^{2+}$와 2.5 mM $Zn^{2+}$에 의하여 각각 925%와 250% 증가되었다. 카드뮴에 의한 카드뮴 적응 MDH의 활성 촉진은 효소반응 4분으로 최대값에 도달했으나, 카드뮴 비적응 MDH의 활성 촉진은 효소 반응 초기인 1분으로 최대값에 도달했다. 카드뮴 적응 MDH와 비적응 MDH의 Km값은 두 효소 모두 6.9 mM L-malate였다. 그러나, 카드뮴 비적응 MDH 활성은 카드뮴에 의하여 Km값이 변화되지 않았고 Vmax만 증가되었으나 카드뮴 적응 MDH 활성은 카드뮴에 의하여 Km값과 Vmax값 모두 변화되었다.