title: Differential effects of metal-binding agents on the D-glucose-6-phosphate phosphohydrolase activity of the rat liver.
abstract: The metal-binding agents (citrate, oxalate, bicarbonate, EDTA) exert dual effects on D-glucose-6-phosphate phosphohydrolase activity in the homogenate as well as in the subcellular fractions. The important differences of the effects are associated with the concentration of the chelator and with time of its addition. The small (appropriate) concentrations of the metal-binding agents stimulate and stabilize the enzyme activity. However, chelators used in higher concentrations exert the inhibitory influence on the activity of glucose-6-phosphatase. Stimulation of the reaction was observed only if the chelator was added before the enzyme-substrate complex formation has been started. The formation of the ternary complex: the enzyme(metal)-chelator substrate exerting a protective influence on the active centre has been suggested. The hypothesis of a similar action of the metal-binding agents and Pi on the glucose-6-phosphatase as a metaloproteid has been proposed.
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology*; D002951:Citrates / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D005952:Glucose-6-Phosphatase / Q000378:metabolism*; D006902:Hydroxymercuribenzoates / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008566:Membranes / Q000187:drug effects / Q000201:enzymology; D008628:Mercury / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D010070:Oxalates / Q000494:pharmacology; D051381:Rats
chemical_list: D001639:Bicarbonates; D002614:Chelating Agents; D002951:Citrates; D006902:Hydroxymercuribenzoates; D010070:Oxalates; D004492:Edetic Acid; D005952:Glucose-6-Phosphatase; D008628:Mercury