title: Glucose-6-phosphate dehydrogenase from Dicentrarchus labrax liver: kinetic mechanism and kinetics of NADPH inhibition.
abstract: The kinetic mechanism of the reaction catalyzed by glucose-6-phosphate dehydrogenase (EC 1.1.1.49) from Dicentrarchus labrax liver was examined using initial velocity studies, NADPH and glucosamine 6-phosphate inhibition and alternate coenzyme experiments. The results are consistent with a steady-state ordered sequential mechanism in which NADP+ binds first to the enzyme and NADPH is released last. Replots of NADPH inhibition show an uncommon parabolic pattern for this enzyme that has not been previously described. A kinetic model is proposed in agreement with our kinetic results and with previously published structural studies (Bautista et al. (1988) Biochem. Soc. Trans. 16, 903-904). The kinetic mechanism presented provides a possible explanation for the regulation of the enzyme by the [NADPH]/[NADP+] ratio.
authors.affiliation: Departamento de Bioquímica y Biologia Molecular y Genética, Universidad de Extremadura, Facultad de Veterinaria, Cáceres, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Bautista
authors.forename: A
authors.initials: A
authors.lastname: Garrido-Pertierra
authors.forename: G
authors.initials: G
authors.lastname: Soler
mesh_terms: D000818:Animals; D001492:Bass; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008433:Mathematics; D009249:NADP / Q000494:pharmacology*; D010084:Oxidation-Reduction
chemical_list: D009249:NADP; D005954:Glucosephosphate Dehydrogenase