Fig. 3. Optimal conditions for XEG12A and XEG74B.

The optimum pH was measured by incubating the reaction mixture at various pH for 20 min at 40 °C (A). For the determination of pH stability the enzymes were pre-warmed in various pH of buffers at 30 °C for 120 min, then remaining activities were measured with xyloglucan as the substrate at pH 7.0 (B). Universal buffer solutions (pH 2.0‒12.0) those were prepared from 0.4 M boric acid / 0.1 M citric acid and 0.2 M trisodium phosphate were used. The optimum temperature was determined by incubating the reaction mixture at various temperature in 40 mM sodium phosphate buffer (pH 7.0) (C). To determine thermal stability the enzymes were pre-heated at 50 °C for various period, then remaining activities were measured with the substrate at 40 °C for 20 min (D, circles). Residual activities after the pre-heating at 60 °C are also shown (triangles). Closed symbols are for XEG12A and open symbols for XEG74B, respectively.