Blumenstein, L.; Domratcheva, T.; Niks, D.; Ngo, H.; Seidel, R.; Dunn, M. F.; Schlichting, I.: BetaQ114N and betaT110V mutations reveal a critically important role of the substrate alpha-carboxylate site in the reaction specificity of tryptophan synthase. Biochemistry 46 (49), S. 14100 - 14116 (2007)