The Pentose Phosphate Pathway

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  • 26.1 The Pentose Phosphate Pathway Yields NADPH and Five-Carbon Sugars

  • 26.2 Metabolism in Context: Glycolysis and the Pentose Phosphate Pathway Are Coordinately Controlled

  • 26.3 Glucose 6-phosphate Dehydrogenase Lessens Oxidative Stress

Growth is an awesome biochemical feat. Two key biochemical components required for growth—ribose sugars and biochemical reducing power—are provided by the pentose phosphate pathway.

Thus far, we have considered glycogen metabolism with a focus on energy production and storage. Another important fate for the ultimate breakdown product of glycogen degradation—glucose 6-phosphate—is as a substrate for the pentose phosphate pathway, a remarkably versatile set of reactions. The pentose phosphate pathway is an important source of NADPH, biosynthetic reducing power. Moreover, the pathway catalyzes the interconversion of the three- and six-carbon intermediates of glycolysis with five-carbon carbohydrates. These interconversions enable the synthesis of pentose sugars required for DNA and RNA synthesis as well as the metabolism of five-carbon sugars consumed in the diet.

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We begin by examining the generation of NADPH, followed by an investigation of the carbohydrate interconversions. We end with a consideration of the versatility of the reactions of the pentose phosphate pathway.