Le système glucose-6 phosphatase hépatique : composantes, propriétés cinétiques, régulation et déficit

Abstract

Glucose 6-phosphatase (G6Pase) catalyzes the last step leading to liver glucose production and is therefore essential to maintain normoglycemia. Given the strategic location of this enzyme at the cross-roads of gluconeogenesis, glycogenolysis and glycolysis, as well as the severe metabolic disorders resulting from different forms of inherited G6Pase deficiency (glycogenosis type 1), studies on the structure-function relationship and regulation of the enzyme are essential to understand glucose metabolism in vivo. In this two models explaining the molecular organization of the G6Pase system are discussed, the conformational model and the substrate transport model, as well as the hormonal regulation of G6Pase and the molecular basis of its pathological deficiency. Our results based on rapid kinetics and specificity of the enzyme for its substrate are in favor of the conformational model. An unidirectional transport of glucose produced by the hydrolysis of G6P has also been revealed in microsomes.