Thermostable tryptophan synthase of Bacillus stearothermophilus expressed in Escherichia coli

The tryptophan synthase genes,trpA andtrpB, from a moderate thermophile,Bacillus stearothermophilus IFO13737, were expressed efficiently inEscherichia coli. The recombinant tryptophan synthase amounted to 22% of the soluble cellular protein, and was purified to homogeneity by three steps. The enzyme is more thermostable thanE.coli tryptophan synthase, especially the α subunit. The enzyme is also more resistant to sodium dodecylsulfate and methanol thanE.coli enzyme.