4-carboxymethyl-4-methylbutenolide mutase

In enzymology, a 4-carboxymethyl-4-methylbutenolide mutase (EC 5.4.99.14) is an enzyme that catalyzes the chemical reaction

4-carboxymethyl-4-methylbut-2-en-1,4-olide ${\displaystyle \rightleftharpoons }$ 4-carboxymethyl-3-methylbut-2-en-1,4-olide

Hence, this enzyme has one substrate, 4-carboxymethyl-4-methylbut-2-en-1,4-olide, and one product, 4-carboxymethyl-3-methylbut-2-en-1,4-olide.

This enzyme belongs to the family of isomerases, specifically those intramolecular transferases transferring other groups. The systematic name of this enzyme class is 4-carboxymethyl-4-methylbut-2-en-1,4-olide methylmutase. Other names in common use include 4-methyl-2-enelactone isomerase, 4-methylmuconolactone methylisomerase, and 4-methyl-3-enelactone methyl isomerase.

• Bruce NC, Cain RB (1988). "beta-Methylmuconolactone, a key intermediate in the dissimilation of methylaromatic compounds by a modified 3-oxoadipate pathway evolved in nocardioform actinomycetes". FEMS Microbiol. Lett. 50: 233–239. doi:10.1111/j.1574-6968.1988.tb02944.x.