To characterise transglycosylation activity, xylotetraose (X4) was used as both donor and acceptor substrate. All RmXyn10A─CM forms were able to synthesise xylo-oligosaccharides (XOS) larger than X4, predominantly accumulating X8 during the 4 h time frame of the experiment (Figs. ). Notably, mutants H69N, N118T and W284H synthesized XOS with higher DP during the disproportionation of 20 mM X4 (Fig. ) than the WT enzyme.