Effect of pH on GOX stability. The residual activities of recombinant (▪), native (•), and deglycosylated (▾) GOXs were measured in 0.1 M sodium acetate buffer, pH 6.0, after 72 h of storage at room temperature in sodium citrate (pH 3.0 to 4.0), sodium acetate (pH 5.0 to 6.0), or Tris-HCl (pH 7.0 to 9.0) (all 50 mM).