[$Hg^{2+} $-induced Reversible Inhibitions of Microsomal $H^+-ATPase$ Prepared from Tomato Roots

$Hg^{2+}$에 의한 토마토 뿌리조직 마이크로솜 $H^+-ATPase$의 가역적 저해

  • Shin, Dae-Seop (Department of Agricultural Chemistry, Chungbuk National University) ;
  • Cho, Kwang-Hyun (Department of Agricultural Chemistry, Chungbuk National University) ;
  • Kim, Young-Kee (Department of Agricultural Chemistry, Chungbuk National University)
  • 신대섭 (충북대학교 농과대학 농화학과) ;
  • 조광현 (충북대학교 농과대학 농화학과) ;
  • 김영기 (충북대학교 농과대학 농화학과)
  • Published : 1999.11.30

Abstract

In order to characterize the effects of heavy metal ions on the microsomal ATPase activities, microsomes were prepared from the roots of tomato plant and the activity of microsomal ATPase was measured by an enzyme-coupled assay. $Hg^{2+}$ inhibited the activity of microsomal ATPase in a dose-dependent manner, while $Gd^{3+}$, $Fe^{3+}$, $La^{3+}$, $Zn^{2+}$, and $Pb^{2+}$ inhibited not only the ATPase activity but also the activities of enzymes used in the assay. However, $Cs^+$ and $Ba^{2+}$ showed no significant effect. $Hg^{2+}$ inhibited the activities of both plasma membrane and vacuolar membrane $H^+-ATPases$. In the dose-response to $Hg^{2+}$, the activities of both microsomal $H^+-ATPases$ were severely inhibited at the concentration of $Hg^{2+}$ above $10\;{\mu}M$ and were completely inhibited at 1 mM $Hg^{2+}$. Apparent Ki values of $Hg^{2+}$ on the inhibitions of plasma membrane and vacuolar membrane $H^+-ATPases$ were $80\;{\mu}M$ and $58\;{\mu}M$, respectively. The $Hg^{2+}$-induced inhibitions were reversible since the addition of dithiothreitol completely reversed the inhibitory effects of $Hg^{2+}$. These results suggest that the inhibitory effects of $Hg^{2+}$ on both plasma, membrane and vacuolar membrane $H^+-ATPases$ are nonselective and reversible.