glucose 6-phosphate, a product of glucokinase ), and is indi- rectly stimulated by glucose (a substrate of glucokinase ) via the following mechanism. Glucokinase regulatory protein (GKRP) in the liver regulates the activity of glucokinase through reversible binding. In the presence of fructose 6- phosphate, glucokinase is translocated into the nucleus and binds tightly to the regulatory protein, thus rendering the enzyme inactive (Figure 8.14). When glucose levels in the blood (and also in the hepatocyte, as a result of GLUT-2) increase, glucokinase is released from the regulatory protein, and the enzyme re-enters the cytosol where it phosphorylates glucose to glucose 6-phosphate. [Note: Fructose 1-phosphate inhibits formation of the glucokinase -GKRP complex.] Glucokinase functions as a glucose sensor in the maintenance of blood glucose homeosta- sis. Mutations that decrease the activity of glu- cokinase are the cause of a rare form of dia- betes, maturity onset diabetes of the young type 2 (MODY 2).