triose

A triose is a simple carbohydrate, or monosaccharide, containing three carbon atoms and the formula C3H6O3. The term covers two main subclasses: aldotriose, which has an aldehyde group at carbon 1, and ketotriose, which has a ketone group at carbon 2.

The best-known aldotriose is glyceraldehyde, which exists as two enantiomers, D- and L-glyceraldehyde, differing at the single chiral center. The primary ketotriose is dihydroxyacetone, which is achiral. Other isomers can arise from different arrangements of the hydroxyl groups on the three carbons, but glyceraldehyde remains the most characteristic aldotriose.

Structurally, triose sugars are the smallest monosaccharides. In aqueous solution, they predominantly exist in the open-chain form; cyclic forms are not stable due to the short carbon chain, so cyclic hemiacetals are not commonly observed for triose sugars.

Biochemically, triose sugars are notable as intermediates in metabolism. The phosphorylated triose sugars glyceraldehyde-3-phosphate and dihydroxyacetone phosphate participate in glycolysis and gluconeogenesis and are interconverted by the enzyme triose phosphate isomerase. As such, they play a central role in energy production and in the provision of carbon frameworks for the biosynthesis of larger carbohydrates.

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