Pentose Phosphate Pathway

Abstract

The pentose phosphate pathway occurs in the cytosol and forms a link between glycolysis and fatty acid as well as nucleotide metabolism.

Keywords: oxidative branch; non‐oxidative branch; glucose‐6‐phosphate dehydrogenase; catecholamines; pathophysiology

Figure 1.

Schematic representation of the oxidative pentose phosphate pathway (centre), its connections to glycolysis (non‐oxidative branch, right‐hand side) via the transaldolase and transketolase reactions (arrows), to synthesis of purine and pyrimidine nucleotide via the de novo synthesis and the salvage pathways, and the routes of degradation of ATP (broken arrows). Abbreviations: G‐1‐P, glucose 1‐phosphate; G‐6‐P, glucose 6‐phosphate; F‐6‐P, fructose 6‐phosphate; F‐1,6‐P, Fructose‐1,6‐bisphosphate; GAP, glyceraldehyde 3‐phosphate; 6‐PGL, 6‐phosphoglucono‐δ‐lactone; 6‐PG, 6‐phosphogluconate; Ru‐5‐P, ribulose 5‐phosphate; R‐5‐P, ribose 5‐phosphate; PRPP, 5‐phosphoribosyl 1‐pyrophosphate; NADP+, nicotinamide–adenine dinucleotide phosphate; IMP, inosine monophosphate; AMP, adenosine monophosphate; ADP, adenosine diphosphate; ATP, adenosine trisphosphate; OMP, orotidine monophosphate; UMP, uridine monophosphate; UDP, uridine diphosphate; UTP, uridine trisphosphate; GSH, reduced glutathione; GSSG, oxidized glutathione; G‐6‐PD, glucose‐6‐phosphate dehydrogenase; 6‐PGD, 6‐phosphogluconate dehydrogenase; GP, glutathione peroxidase; GR, glutathione reductase; SOD, superoxide dismutase; XD, xanthine dehydrogenase; XO, xanthine oxidase.

Figure 2.

Activity of glucose‐6‐phosphate dehydrogenase (top), availability of the pool of 5‐phosphoribosyl 1‐pyrophosphate (middle), and rates of the de novo synthesis of adenine nucleotides (bottom) in several rat organs. Data are mean values ± SEM; number of experiments in parentheses (modified from Zimmer H‐G, Ibel H and Suchner U (1990) Circulation Research67: 1525–1534).

Figure 3.

Reactions of the classical non‐oxidative pentose phosphate pathway involving transketolase and transaldolase to connect ribose 5‐phosphate to glycolysis.

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References

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Further Reading

Glock GE and McLean P (1954) Levels of enzymes of the direct oxidative pathway of carbohydrate metabolism in mammalian tissues and tumours. Biochemical Journal 56: 171–175.

Lee RGL, Springer C, Kasulis P et al. (1987) Nuclear magnetic resonance assessment of adenosine triphosphate (ATP) dynamics in ischemic mouse livers perfused with adenine and ribose. Investigative Radiology 22: 685–687.

McAnulty JF, Southard JH and Belzer FO (1987) Improved maintenance of adenosine triphosphate in five‐day perfused kidneys with adenine and ribose. Transplantation Proceedings 19: 1376–1379.

Meijer AE (1991) The pentose phosphate pathway in skeletal muscle under pathophysiological conditions. A combined histochemical and biochemical study. Progress in Histochemistry and Cytochemistry 22: 1–118.

Seymour A‐ML, Eldar H and Radda GK (1990) Hyperthyroidism results in increased glycolytic capacity in the rat heart. A 31P‐NMR study. Biochimica et Biophysica Acta 1055: 107–116.

Wagner KR, Kauffman FC and Max SR (1978) The pentose phosphate pathway in regenerating skeletal muscle. Biochemical Journal 170: 17–22.

Williams JF and Blackmore PF (1983) Non‐oxidative synthesis of pentose 5‐phosphate from hexose 6‐phosphate and triose phosphate by the L‐type pentose pathway. International Journal of Biochemistry 15: 797–816.

Zimmer H‐G and Schneider A (1991) Nucleotide precursors modify the effects of isoproterenol. Studies on heart function and cardiac adenine nucleotide content in intact rats. Circulation Research 69: 1575–1582.

Zimmer H‐G, Ibel H and Suchner U (1990) β‐Adrenergic agonists stimulate the oxidative pentose phosphate pathway in the rat heart. Circulation Research 67: 1525–1534.

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Zimmer, Heinz‐Gerd(Apr 2001) Pentose Phosphate Pathway. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001365]