D-Xylulose is a ketopentose, a monosaccharide containing five carbon atoms and a ketone functional group. It is converted from xylitol in the glucoronate-xylulose pathway. D-Xylulokinase catalyzes the ATP-dependent phosphorylation of D-xylulose to produce xylulose 5-phosphate, which is linked to the pentose-phosphate pathway.