Mammalian hexokinases: a system for the study of co-operativity in monomeric enzymes

Kinetic and structural studies have been carried out of two isoenzymes of hexokinase from the rat, hexokinase II and glucokinase. Although both enzymes are monomeric, hexokinase II has a molecular weight double that of glucokinase and resembles a dimer of glucokinase. The co-operativity of glucokinase, which is not observed for hexokinase II, appears to be kinetic in origin rather than the consequence of ineractions between distinct glucose-binding sites.