Figure 7. Effect of pH on the activity and stability of GF-Spr1.

(a) Effect of pH on enzyme activity. To determine the optimum pH for the enzyme activity, standard assay mixtures in 50 mM of the following buffers were used at 30ºC: sodium acetate, pH 3.4 - 5.66; MES, pH 5.15 - 7.22; Tris-HCl, pH 7.13 - 8.9; CHES, pH 8.17 - 10.28 and CAPS, pH 9.4 - 11.39. The highest activity observed at pH 8.5 was defined as 100% activity and other activity levels were calculated relative to this value.

(b) Effect of pH on enzyme stability. The pH stability was determined by measuring the remaining activity of the enzyme after incubating the enzyme at 30ºC for 30 min with 10 mM of all the above mentioned buffers and an additional buffer, Citrate, pH 2.17 - 4.1.