Functional classification and biochemical characterization of a novel rho class glutathione S-transferase in Synechocystis PCC 6803

• A novel class of glutathione S-transferase (GST) is reported.
• This GST catalyzes dichloroacetate (DCA) degradation and hydroperoxide reactions.
• Functionally this GST is similar to zeta and theta/alpha classes but structurally very different.
• In contrast to other bacterial GSTs, this GST exists as a monomer in solution.
• First report of DCA degradation by any bacterial GST and has potential biotechnological applications.

We report a novel class of glutathione S-transferase (GST) from the model cyanobacterium Synechocystis PCC 6803 (sll1545) which catalyzes the detoxification of the water pollutant dichloroacetate and also shows strong glutathione-dependent peroxidase activity representing the classical activities of zeta and theta/alpha class respectively. Interestingly, sll1545 has very low sequence and structural similarity with these classes. This is the first report of dichloroacetate degradation activity by any bacterial GST. Based on these results we classify sll1545 to a novel GST class, rho. The present data also indicate potential biotechnological and industrial applications of cyanobacterial GST in dichloroacetate-polluted areas.