In enzymology, a hydroxyacid-oxoacid transhydrogenase () is an enzyme that catalyzes the chemical reaction (S)-3-hydroxybutanoate + 2-oxoglutarate acetoacetate + (R)-2-hydroxyglutarate Thus, the two substrates of this enzyme are (S)-3-hydroxybutanoate and 2-oxoglutarate, whereas its two products are acetoacetate and (R)-2-hydroxyglutarate. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with other acceptors. The systematic name of this enzyme class is (S)-3-hydroxybutanoate:2-oxoglutarate oxidoreductase. This enzyme is also called transhydrogenase, hydroxy acid-oxo acid. See also D2HGDH L2HGDH 2-hydroxyglutarate synthase 2-hydroxyglutarate dehydrogenase Alpha-Hydroxyglutaric acid 2-Hydroxyglutaric aciduria References EC 1.1.99 Enzymes of unknown structure