Regulates glucokinase (gck) by forming an inactive complex with this enzyme (PubMed:23733961). 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 (PubMed:23733961). Interacts (fructose 6-phosphate bound form) with gck. Fructose 1-phosphate and fructose 6-phosphate compete for the same binding site. Belongs to the GCKR family.