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After ingestion, fructose is converted to fructose-1-phosphate in the liver by fructokinase. Deficiencies of fructokinase cause essential fructosuria, a clinically benign condition characterized by the excretion of unmetabolized fructose in the urine. Fructose-1-phosphate is metabolized by aldolase B into dihydroxyacetone phosphate and ...
The lack of two important enzymes in fructose metabolism results in the development of two inborn errors in carbohydrate metabolism – essential fructosuria and hereditary fructose intolerance. In addition, reduced phosphorylation potential within hepatocytes can occur with intravenous infusion of fructose.
Hereditary fructose intolerance (HFI) results in poor feeding, failure to thrive, chronic liver disease and chronic kidney disease, and death. HFI is caused by a deficiency of fructose 1,6-biphosphate aldolase in the liver, kidney cortex and small intestine. Infants and adults are asymptomatic unless they ingest fructose or sucrose. [citation ...
In hereditary fructose intolerance caused by defects in aldolase B, fructose 1-phosphate accumulates in the liver and causes a number of adverse defects. Hypoglycemia results from inhibition of glycogenolysis and gluconeogenesis.
Aldolase B is a homotetrameric enzyme, composed of four subunits with molecular weights of 36 kDa with local 222 symmetry. Each subunit has a molecular weight of 36 kDa and contains an eight-stranded α/β barrel, which encloses lysine 229 (the Schiff-base forming amino acid that is key for catalysis).
The amount of fructose routinely lost in urine is quite small. [6] Other errors in fructose metabolism have greater clinical significance. Hereditary fructose intolerance, or the presence of fructose in the blood (fructosemia), is caused by a deficiency of aldolase B, the second enzyme involved in the metabolism of fructose. [citation needed]
Fructose malabsorption, formerly named dietary fructose intolerance (DFI), is a digestive disorder [1] in which absorption of fructose is impaired by deficient fructose carriers in the small intestine's enterocytes. This results in an increased concentration of fructose. Intolerance to fructose was first identified and reported in 1956. [2]
Fructose intolerance may refer to: Fructose malabsorption , a digestive disorder of the small intestine in which the fructose carrier in enterocytes is deficient Hereditary fructose intolerance , a hereditary condition caused by a deficiency of liver enzymes that metabolise fructose