Triosephosphate isomerase of the hyperthermophile Thermoproteus tenax:: thermostability is not everything

triosephosphate isomerase of the hyperthermophilic crenarchaeum Thermoproteus tenax (TtxTIM) represents a homomeric tetramer. Unlike the triosephosphate isomerases of other hyperthermophiles, however, the association of the TtxTIM tetramers is looser, allowing a reversible dissociation into inactive dinners. The dimer/tetramer equilibrium of TtxTIM is shifted to the tetrameric state through a specific interaction with glycerol-1-phosphate dehydrogenase of T. tenax, suggesting that higher oligornerization of the TtxTIM serves functional rather than stabilizing purposes.