Fructose1phosphate

Fructose-1-phosphate (F1P) is a phosphorylated derivative of the sugar fructose. It is formed in cells by the enzyme fructokinase (ketohexokinase) through phosphorylation of fructose at the C-1 position, yielding fructose-1-phosphate. In humans this reaction occurs mainly in the liver, but also in the kidney and small intestine after dietary fructose intake.

F1P is an intermediate in the fructose catabolic pathway. Aldolase B cleaves fructose-1-phosphate into dihydroxyacetone phosphate (DHAP) and glyceraldehyde. The glyceraldehyde is subsequently phosphorylated by triose kinase to glyceraldehyde-3-phosphate, which can enter glycolysis or gluconeogenesis. This pathway bypasses the phosphofructokinase step of glycolysis, allowing rapid metabolism of fructose but also potentially creating metabolic bottlenecks under high fructose loads.

Clinical significance includes hereditary fructose intolerance (HFI), caused by aldolase B deficiency. In HFI, accumulation of fructose-1-phosphate depletes cellular phosphate and inhibits glycogenolysis and gluconeogenesis, leading to hypoglycemia, vomiting, abdominal pain, jaundice, and hepatomegaly after fructose ingestion. Another condition, essential fructosuria, results from fructokinase deficiency and is usually benign, characterized by fructose excretion in the urine. Diagnosis of HFI relies on clinical history, biochemical tests, and genetic analysis; management involves restricting fructose, sucrose, and sorbitol from the diet.