Glucose-6-phosphate dehydrogenase from Dicentrarchus labrax liver: kinetic mechanism and kinetics of NADPH inhibition |
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Authors: | JosM Bautista Amando Garrido-Pertierra Germn Soler |
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Institution: | JoséM. Bautista, Amando Garrido-Pertierra,Germán Soler, |
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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. |
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Keywords: | Glucose-6-phosphate dehydrogenase Kinetic mechanism NADPH inhibition (D labrax) |
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