Overview fructose Source sucrose in fruits and sweeteners disaccharide of glucose and fructose hydrolyzed by sucrase in brush border of small intestine Pathway liver is main site of metabolism also in renal proximal tubule DHAP and glyceraldehyde enter into glycolysis downstream of regulation Clinical relevance fructokinase deficiency benign presentation fructosuria does not have the osmotic pathologies (e.g. cataracts) associated with galactokinase deficiencies fructose is not an aldose and therefore not substrate for aldose reductase fructose 1-P aldolase (aldolase B) deficiency aka hereditary fructose intolerance AR more severe than fructokinase deficiency because fructose 1-P acts as a phosphate sink presentation fructosuria lethargy hypoglycemia liver and proximal renal tubule disorder hyperbilirubinemia hyperuricemia degradation of ADP due to loss of Pi treatment fructose (and sucrose)-free diet