Activity assay of alanine-mutants. Shown is the mean product concentration with standard deviation of three independent samples. For the assay, 0.01 mmol*L-1 Strep-purified mutants, 50 mmol*L-1 Tris-HCl pH 8 and 20 mmol*L-1 substrate 1 were incubated at room temperature and 400 rpm for 24 h. Samples were extracted 1 : 1 with isohexane for gas chromatography. ctrl=buffer and substrate only.
