title: Substrate form of D-frutose 1,6-bisphosphate utilized by fructose 1,6-bisphosphatase.
abstract: Rapid quench kinetic experiments on fructose 1,6-bisphosphatase demonstrate a stereospecificity for the alpha anomer of fructose 1,6-bisphosphate relative to the beta configuration. The beta anomer is only utilized after mutarotation to the alpha form in a process that is not enzyme catalyzed. Studies employing analogues of the acyclic keto configuration indicate that the keto form is utilized at a rate less than 5% that of the alpha anomer, a finding also confirmed by computer simulation of the rapid quench data. Chemical trapping experiments of the keto analogue, xylulose 1,5-bisphosphate, and the normal substrate suggest that interconversion of the acyclic and anomeric configurations is retarded by their binding to the enzyme. A hypothesis is advanced attributing substrate inhibition of fructose 1,6-bisphosphatase to possible binding of the keto species.
mesh_terms: D001894:Borohydrides; D003201:Computers; D004099:Dihydroxyacetone Phosphate / Q000032:analysis; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D005636:Fructosephosphates / Q000032:analysis; D005994:Glycerophosphates / Q000032:analysis; D007536:Isomerism; D007700:Kinetics; D008956:Models, Chemical; D010428:Pentosephosphates; D010756:Phosphoric Acids / Q000032:analysis; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014996:Xylulose
chemical_list: D001894:Borohydrides; D005636:Fructosephosphates; D005994:Glycerophosphates; D010428:Pentosephosphates; D010756:Phosphoric Acids; D004099:Dihydroxyacetone Phosphate; D014996:Xylulose; D006597:Fructose-Bisphosphatase