MALDI-TOF mass spectra of xylooligosaccharides generated by xylanase digestion of xylan from the <i>gxm1/2/3</i> mutant overexpressing PtrGXMs.

<p>The ions at <i>m/z</i> 745 and 759 are attributed to xylotetrasaccharides bearing a GlcA residue [(GlcA)Xyl₄] and a methylated GlcA residue [(MeGlcA)Xyl₄], respectively. The ion at <i>m/z</i> 761 corresponds to the xylan reducing end pentasaccharide, β-d-Xyl-(1→4)-β-d-Xyl-(1→3)-α-l-Rha-(1→2)-α-d-GalA-(1→4)-d-Xyl (X-X-R-GA-X). Note the partial restoration of the ion signal at <i>m/z</i> 759 corresponding to (MeGlcA)Xyl₄ (red arrows) in the <i>gxm1/2/3</i> mutant overexpressing PtrGXMs.