Disorders of fructose metabolism (WP5178)

Fructose is converted into fructose-1-phosphate, this reaction is facilitated by fructokinase (also called ketohexokinase)(encoded by KHK). Connected to this reaction is the metabolic disease "essential fructosuria" which causes a deficiency in fructokinase. After this fructose-1-phosphate is converted into glyceraldehyde and dihydroxyacetone-phosphate, this is facilitated by aldolase B (encoded by ALDOB). connected to this reaction is the metabolic disease "hereditary fructose intolerance", which is the result of the absence of aldolase B. The glyceraldehyde produced from this reaction will be converted into D-glycerate through the activity of Aldehyde dehydrogenase 1 family, member A1 or ALDH1A1 (encoded by the ALDH1A1 gene). The D-glycerate will be converted (according to the book) into 2-Phosphoglyceric acid through the activity of Glycerate kinase (encoded by GLYCTK), connected to this reaction is the metabolic disease "glycerate kinase deficiency" which results in the accumulation of D-glycerate. The resulting 2-phosphoglyceric acid then goes through a series of reactions resulting in pyruvate. Another entry into this pathway is through the conversion of glucose-6-phosphate into fructose-6-phosphate through glucose-6-phosphate isomerase (encoded by GPI). The fructose-6-phosphate can be converted into fructose-1,6-biphosphate through phosphofructokinase (encoded by PFKL). Fructose-1,6-biphosphate can be converted into fructose-6-phosphate by fructose-1,6-biphosphatase, connected to this reaction is the metabolic disease "Fructose-1,6-biphosphatase deficiency". When going further, the fructose-1,6-biphosphate is converted into dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate through the activity of aldolase B, this reaction is also affected by hereditary fructose intolerance. The glyceraldehyde-3-phosphate is then eventually turned into pyruvate through a series of reactions. The dihydroxyacetone-phosphate resulting from the aldolase B involved reactions can be converted into glyceraldehyde-3-phosphate through the activity of triose-phosphate isomerase (encoded by TPI1). This pathway is based on the fructose metabolism pathway (Chapter 18, Figure 18.5) in the book Physicians Guide to the Diagnosis, Treatment, and Follow-Up of Inherited Metabolic Diseases (ed. 4) by Nenad Blau, Marinus Duran, K Michael Gibson, Carlo Dionisi.(ISBN 3642403360 (978-3642403361))

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