title: Affinity of glucose analogs for alpha-glucan phosphorylases from rabbit muscle and potato tubers.
abstract: The action of phosphorylase b from rabbit muscle and potato phosphorylase was inhibited to various extents by several glucose analogs. Like glucose itself, all of the glucosidic oxygen-substituted analogs tested in kinetic experiments showed a nonlinear competitive inhibition for muscle phosphorylase b and a linear competitive one for potato phosphorylase. 5-Thio-D-glucose, one of the ring oxygen-substituted analogs, also inhibited the action of muscle phosphorylase b in the same manner, while the inhibition pattern of 5-amino-D-glucose (nojirimycin) was of a linear noncompetitive type. Since the conformation of 5-amino-D-glucose in aqueous solution is half-chair (Reese et al. (1971) Carbohyd. Res. 18, 381-388), the unusual kinetic behavior of the compound toward muscle phosphorylase b was supposed to be due to its half-chair conformation. In the glucosidic oxygen-substituted analogs, the affinity for both muscle phosphorylase b and potato phosphorylase decreased with decreasing order of magnitude of electronegativity of the glucosidic atom. The strong positive correlation between the affinity and the electronegativity suggests that D-glucose-1-P, the substrate, may bind to phosphorylase with the formation of a hydrogen bond between its glucosidic oxygen and a hydrogen donor of the enzyme.
mesh_terms: D017485:1-Deoxynojirimycin / Q000031:analogs & derivatives; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D005459:Fluorides / Q000494:pharmacology; D005944:Glucosamine / Q000494:pharmacology; D005947:Glucose / Q000031:analogs & derivatives* / Q000494:pharmacology; D005958:Glucosephosphates / Q000494:pharmacology; D007536:Isomerism; D007700:Kinetics; D008968:Molecular Conformation; D009132:Muscles / Q000201:enzymology*; D006005:Phosphorylases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D011817:Rabbits; D013329:Structure-Activity Relationship
chemical_list: D005958:Glucosephosphates; D017485:1-Deoxynojirimycin; C003002:5-thio-D-glucose; D000249:Adenosine Monophosphate; D006005:Phosphorylases; D005947:Glucose; D005944:Glucosamine; D005459:Fluorides; C013626:nojirimycin