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

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

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.

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 $Cd^{2+}$.