Effect of pH on enzyme stability. The enzyme was incubated at 20°C in pH 5.0 to 7.0 100 mM buffers for a period of time. After that, residual activity was assayed in optimal temperature and pH by DNS method. Closed triangles squares and rhombuses represent AbnZ1 at pH 7.0 Na-phosphate, pH 6.0 Na-acetate, and pH 5.0 Na-acetate. The highest activity was taken as 100%. Reaction substrate was 0.25% red debranched arabinan (a) pH stability of AbnZ2. (b) pH stability of AbnZ3.