Activation of a GH43 β-xylosidase by divalent metal cations: Slow binding of divalent metal and high substrate specificity

- RS223-BX is strongly activated by Ca2+, Co2+, Fe2+, Mg2+, Mn2+ and Ni2+.
- The β-xylosidase is inactivated by Cu2+ and Zn2+.
- E binds Mg2+, E Mg2+ isomerizes slowly to E∗ Mg2+ and E∗ Mg2+ binds substrate.
- Metal-activated RS223-BX exhibits the highest known kcat/Km on xylooligosaccharides.
- RS223-BX has potential use in the saccharification of xylan for fermentation purposes.