In enzymology, dimethylmalate dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are (R)-3,3-dimethylmalic acid and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are ñ-ketoisovaleric acid, carbon dioxide, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is (R)-3,3-dimethylmalate:NAD<sup>+</sup> oxidoreductase (decarboxylating). This enzyme is also called beta,beta-dimethylmalate dehydrogenase. This enzyme participates in pantothenate and coa biosynthesis. It has 5 cofactors: ammonia, manganese, cobalt, potassium, and NH<sub>4</sub><sup>+</sup>.