process

Fructose metabolism

Fructose metabolism is best understood by considering three enzymes: fructokinase, fructose-bisphosphate aldolase B, and adenosine triphosphate (ATP)-dependent dihydroxyacetone kinase (or triokinase). All three of these are only found in the liver and kidneys of rats and humans. In the liver, fructose is rapidly converted to fructose 1-phosphate via fructokinase. Fructose 1-phosphate is then converted into the trioses dihydroxyacetone phosphate and glyceraldehyde via aldolase B. Aldolase B also functions in the liver for normal glycolysis (glucose metabolism). Glyceraldehyde is then converted to glyceraldehyde-3-phosphate via triokinase. Up until this point in fructose metabolism, there have been no rate-limiting steps and, as a result, there is an increased amount of substrate leading to metabolic pathways from triose phosphate (i.e. glycolysis, glycogenesis, glyconeogenesis, lipogenesis, and fatty acid esterification). Glyceraldehyde-3-phosphate is next metabolized to pyruvate via the rate-limiting enzyme, pyruvate kinase. Fructose enhances the activation of pyruvate kinase and thus leads to an increased flux of pyruvate into the Krebs’s cycle. It should be noted that fructose metabolism does not promote an insulin response (Fig. 19.1).

Ref:
Eric Campbell, Anna Schlappal, Eliana Geller, Thomas W. Castonguay, Chapter 19 - Fructose-Induced Hypertriglyceridemia: A Review, Editor(s): Ronald Ross Watson, Nutrition in the Prevention and Treatment of Abdominal Obesity, Academic Press, 2014, Pages 197-205, ISBN 9780124078697, https://doi.org/10.1016/B978-0-12-407869-7.00019-2. (https://www.sciencedirect.com/science/article/pii/B9780124078697000192)

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Added on Sep 27, 2022 by Barbara Van De Keer
Edited on Sep 28, 2022 by Barbara Van De Keer

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