F1p

F1p, typically written as F1P, refers to fructose-1-phosphate, a phosphorylated sugar intermediate formed during the metabolism of fructose. In humans, fructose is mainly processed in the liver, where the enzyme fructokinase converts fructose to fructose-1-phosphate (F1P). From there, F1P enters the glycolytic pathway through subsequent enzymatic steps.

The primary metabolic pathway involves the enzyme aldolase B, which cleaves F1P into dihydroxyacetone phosphate (DHAP) and glyceraldehyde. The glyceraldehyde is then phosphorylated to glyceraldehyde-3-phosphate (G3P) by triose kinase. This route connects fructose metabolism to glycolysis, allowing rapid production of triose phosphates. Unlike glucose metabolism, the initial fructose step bypasses the regulatory phosphofructokinase-1 (PFK-1) checkpoint, a feature that has implications for metabolic control, especially when fructose intake is high.

Clinical relevance is most pronounced in hereditary fructose intolerance (HFI), a genetic deficiency of aldolase B. In HFI, accumulation of F1P can sequester phosphate and impair energy homeostasis, inhibiting glycogen breakdown and gluconeogenesis. This leads to hypoglycemia, vomiting, and abdominal pain after ingestion of fructose, sucrose, or sorbitol. Management focuses on dietary restriction of these sugars.

In research and clinical practice, F1P serves as a key marker in studies of fructose metabolism and related disorders. Analytical approaches include enzymatic assays and chromatographic methods. While F1P is its most common meaning, the abbreviation may appear in other technical contexts, so clear definition is advisable.