Regulates glucokinase (GCK) by forming an inactive complex with this enzyme (PubMed:10713097). Acts by promoting GCK recruitment to the nucleus, possibly to provide a reserve of GCK that can be quickly released in the cytoplasm after a meal (PubMed:10713097). The affinity of GCKR for GCK is modulated by fructose metabolites: GCKR with bound fructose 6-phosphate has increased affinity for GCK, while GCKR with bound fructose 1-phosphate has strongly decreased affinity for GCK and does not inhibit GCK activity (By similarity). Interacts (fructose 6-phosphate bound form) with GCK. Under low glucose concentrations, GCKR associates with GCK and the inactive complex is recruited to the hepatocyte nucleus. Fructose 1-phosphate and fructose 6-phosphate compete for the same binding site. Mice appear normal and are fertile (PubMed:10713097). Their body weights do not differ significantly from the body weights of wild-type animals up to 60 weeks of age (PubMed:10713097). Mice however show a substantial decrease in hepatic glucokinase (Gck) expression and enzymatic activity, with no change in basal blood glucose levels (PubMed:10713097). However, following a glucose tolerance test, mice show impaired glucose clearance, possibly because they cannot recruit sufficient glucokinase due to the absence of a nuclear reserve (PubMed:10713097). Belongs to the GCKR family.