In enzymology, a formaldehyde transketolase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are D-xylulose 5-phosphate and formaldehyde, whereas its two products are glyceraldehyde 3-phosphate and glycerone.
This enzyme belongs to the family of transferases, specifically those transferring aldehyde or ketonic groups (transaldolases and transketolases, respectively). The systematic name of this enzyme class is D-xylulose-5-phosphate:formaldehyde glycolaldehydetransferase. This enzyme is also called dihydroxyacetone synthase. This enzyme participates in methane metabolism. It employs one cofactor, thiamin diphosphate.