Fructose Metabolism

1. Phosphorylation of fructose in most tissues yields fructose-6-phosphate, a glycolytic intermediate.

2. A different pathway is involved in vertebrate liver, where the enzyme fructokinase phosphorylates fructose to fructose-1-phosphate (F1P). This intermediate is then cleaved by a specific enzyme, aldolase B. Cleavage products are dihydroxyacetone phosphate, a glycolytic intermediate, and D-glyceraldehyde. The latter is then phosphorylated in an ATP-dependent reaction to give the glycolytic intermediate glyceraldehyde-3-phosphate. This pathway of utilization bypasses regulation and may account for the ease with which dietary sucrose is converted to fat.

See also: Sucrose