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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 ...
Hexokinase IV (Glucokinase), also occurs in the liver and would be capable of phosphorylating fructose to fructose 6-phosphate (an intermediate in the gluconeogenic pathway); however, it has a relatively high Km (12 mM) for fructose and, therefore, essentially all of the fructose is converted to fructose-1-phosphate in the human liver.
This enzyme deficiency results in an accumulation of fructose-1-phosphate, which inhibits the production of glucose and results in diminished regeneration of adenosine triphosphate. Clinically, patients with hereditary fructose intolerance are much more severely affected than those with essential fructosuria, with elevated uric acid , growth ...
Hepatic fructokinase (or ketohexokinase) is an enzyme that catalyzes the phosphorylation of fructose to produce fructose-1-phosphate. ATP + {\displaystyle \longrightarrow } ADP + ATP + D-fructose → ADP + D-fructose-1-phosphate [ 1 ]
Frk 2 has a higher affinity for fructose than Frk 1 but Frk 2 activity is inhibited by high levels of fructose, whereas Frk 1 activity is not. [ 2 ] In Sinorhizobium meliloti , a common gram-soil bacterium, fructokinase is also used in the metabolism of mannitol and sorbitol, in addition to the metabolism of fructose.
6-phosphofructokinase, liver type (PFKL) is an enzyme that in humans is encoded by the PFKL gene on chromosome 21. [5] This gene encodes the liver (L) isoform of phosphofructokinase-1 , an enzyme that catalyzes the conversion of D - fructose 6-phosphate to D - fructose 1,6-bisphosphate , which is a key step in glucose metabolism ( glycolysis ).
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]
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 ...