Xylose Isomerase catalyzes the reversible isomerization of D-glucose and D-xylose to D-fructose and D-xylulose, respectively. It is widely used in the food industry for the production of the sweetener High Fructose Corn Syrup (HFCS) from corn starch. The enzyme is one of the three highest tonnage value enzymes, amylase and protease being the other two. The enzyme works in your small intestine, In the small intestine the enzyme establishes an equilibrium between fructose and glucose in the food mash. In this way you can absorb the glucose, and the fructose and glucose can be absorbed together through the intestinal wall (1:1 ratio).