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Pentose Phosphate Pathway of Glucose Oxidation:- Glucose 6-Phosphate Is Partitioned between Glycolysis and the Pentose Phosphate Pathway

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  554

2026-06-04

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Pentose Phosphate Pathway of Glucose Oxidation:- Glucose 6-Phosphate Is Partitioned between Glycolysis and the Pentose Phosphate Pathway

Whether glucose 6-phosphate enters glycolysis or the pentose phosphate pathway depends on the current needs of the cell and on the concentration of NADP in the cytosol. Without this electron acceptor, the first reaction of the pentose phosphate pathway (catalyzed by G6PD) cannot proceed. When a cell is rapidly con verting NADPH to NADP in biosynthetic reductions, the level of NADP rises, allosterically stimulating G6PD and thereby increasing the flux of glucose 6-phosphate through the pentose phosphate pathway (Fig. 14–27). When the demand for NADPH slows, the level of NADP drops, the pentose phosphate pathway slows, and glucose 6-phosphate is instead used to fuel glycolysis.

FIGURE 14–27 Role of NADPH in regulating the partitioning of glucose 6-phosphate between glycolysis and the pentose phosphate pathway. When NADPH is forming faster than it is being used for biosynthesis and glutathione reduction (see Fig. 14–20), [NADPH] rises and inhibits the first enzyme in the pentose phosphate pathway. As a result, more glucose 6-phosphate is available for glycolysis.

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