Glutathione S-Transferase Activities of S-Type and L-Type Thioltransferases from Arabidopsis thaliana

  • Cho, Young-Wook (Division of Life Sciences, Kangwon National University) ;
  • Park, Eun-Hee (College of Pharmacy, Sookmyung Women's University) ;
  • Lim, Chang-Jin (Division of Life Sciences, Kangwon National University)
  • Received : 0
  • Accepted : 0
  • Published : 0

Abstract

The glutathione S-transferase (GST) activities of S-type and L-type thioltransferases (TTases), which are purified from the seeds and leaves of Arabidopsis thaliana, respectively, were identified and compared. The S-type and L-type TTases showed $K_m$ values of 9.72 mM and 3.18mM on 1-chloro-2,4-dinitrobenzene (CDNB), respectively, indicating the L-type TTase has higher affinity for CDNB. The GST activity of the L-type TTase was rapidly inactivated after being heated at $70^{\circ}C$ or higher. The GST activity of the S-type TTase remains active in a range of $30-90^{\circ}C$. $Hg^{2+}$ inhibited the GST activity of the S-type TTase, whereas $Ca^{2+}$ and $Cd^{2+}$ inhibited the GST activity of the L-type TTase. Our results suggest that the GST activities of two TTases of Arabidopsis thaliana may have different catalytic mechanisms. The importance of the co-existence of TTAse and GST activities in one protein remains to be elucidated.