In order to understand the mechanism behind the manifestation of the symptoms of glucose-6-phosphate dehydrogenase deficiency, we should look at the biochemistry of glucose metabolism, paying particular attention to the hexose monophosphate pathway (HMP) and the role of glucose-6-phosphate dehydrogenase as the first enzyme in this pathway. 4.(Figure 2) Glucose-6-phosphate dehydrogenase is a polypeptide of 515 amino acids, built up of identical subunits, with molecular weight of 59,265 each. The enzyme is rich in sulfhydryl groups (-SH) containing eleven -SH's per subunit. 1.
In a red blood cell which is not oxidatively stressed, about 90% of glucose is metabolised along the anaerobic Embden-Meyerhof pathway and the other 10% or so is metabolised aerobically along the hexose monophosphate pathway. 1.In the hexose monophosphate pathway, glucose-6-phosphate dehydrogenase forms most of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) in cells which is necessary for the reactions of various biosynthetic pathways, the stability of catalase and the regeneration of reduced glutathione (GSH) from the oxidised glutathione (GSSG).(Figure 3) The reduced form of NADPH, catalase and GSH are the main antioxidants of cells. In this way glucose-6-phosphate dehydrogenase provides a source of reducing power in the form of sulfhydryl buffers that maintains the integrity of protein and lipid sulfhydryl groups and aids in the detoxification of free radicals and peroxides. 3. 4. 6. 7.
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Prepared on 01 Jan 2008 by teekoonhien |
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