Fig. 1

Two common xylose metabolism pathways in microorganisms. Xylose can be directly converted to xylulose by a xylose isomerase (XI) or converted to xylitol by a xylose reductase (XR). Xylitol is then converted to xylulose by a xylitol dehydrogenase (XD). Both the XR and XD reactions require co-factors. Xylulose is then converted to xylulose-5-phosphate by an ATP-dependent xylulose kinase (XK)