Indole-3-glycerol-phosphate synthase from Sulfolobus solfataricus as a model for studying thermostable TIM-barrel enzymes.

Indole-3-glycerol-phosphate synthase, a thermophilic and thermostable enzyme from the archaeon Sulfolobus solfataricus, was purified and characterized. The sequence of the thermophilic enzyme was compared to the sequence of a homologous mesophilic enzyme from Escherichia coli. The secondary structure of the thermophilic enzyme was predicted taking into account the patterns of hydropathy, chain flexibility and amphipathicity and the CD spectrum. From this analysis it turned out that indole-3-glycerol-phosphate synthase from S. solfataricus can be considered a model for studying thermostable TIM-barrel enzymes. Some peculiarities of the amino-acid sequence of indole-3-glycerol-phosphate synthase from S. solfataricus are discussed in relation to the thermostability of the enzyme.