Fig 3.

Effect of pH on the isoleucine 2-epimerase activity with l-Ile (A) and d-allo-Ile (B) as the substrates. The buffers used were sodium citrate (pH 3.5 to 6.0) (open circles), MES (morpholineethanesulfonic acid)-NaOH (pH 6.0 to 7.0) (solid circles), HEPES-NaOH (pH 7.0 to 8.0) (open squares), TAPS {3-([2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-amino)-1-propanesulfonic acid}-NaOH (pH 8.0 to 9.0) (solid squares), and CHES (N-cyclohexyl-2-aminoethanesulfonic acid)-NaOH (pH 9.0 to 10.0) (open triangles). Enzyme activities are expressed as percentages relative to 156 μmol·mg⁻¹·min⁻¹ (A) and 233 μmol·mg⁻¹·min⁻¹ (B), which are shown as 100%. All values were obtained through repeated measurements (n = 3).