In enzymology, a 2-acetolactate mutase (EC 5.4.99.3) is an enzyme that catalyzes the chemical reaction

2-acetolactate ${\displaystyle \rightleftharpoons }$ 3-hydroxy-3-methyl-2-oxobutanoate

Hence, this enzyme has one substrate, 2-acetolactate, and one product, 3-hydroxy-3-methyl-2-oxobutanoate.

This enzyme belongs to the family of isomerases, specifically those intramolecular transferases transferring other groups. The systematic name of this enzyme class is 2-acetolactate methylmutase. Other names in common use include acetolactate mutase, and acetohydroxy acid isomerase. This enzyme participates in valine, leucine and isoleucine biosynthesis.

• Allaudeen HS, Ramakrishnan T (1968). "Biosynthesis of isoleucine and valine in Mycobacterium tuberculosis H37 Rv". Arch. Biochem. Biophys. 125 (1): 199–209. doi:10.1016/0003-9861(68)90655-3. PMID 4384955.