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

초록

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<inf>m</inf>, values of 9.72 mM and 3.18 mM 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°C or higher. The GST activity of the S-type TTase remains active in a range of 30-90°C. Hg2+ inhibited the GST activity of the S-type TTase, whereas Ca2+ and Cd2+ 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.

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