Ketohexokinase (fructokinase, KHK) catalyzes the phosphorylation of fructose to fructose-1-phosphate (F1P), the first step in the metabolism of dietary fructose. KHK can also phosphorylate several other furanose sugars []. It is found in higher eukaryotes where it is believed to function as a dimer and requires K(+) and ATP to be active []. In humans, hepatic KHK deficiency causes fructosuria, a benign inborn error of metabolism [, ].