In enzymology, a 1,2-dihydroxy-6-methylcyclohexa-3,5-dienecarboxylate dehydrogenase (EC 1.3.1.68) is an enzyme that catalyzes the chemical reaction

1,2-dihydroxy-6-methylcyclohexa-3,5-dienecarboxylate + NAD⁺ ${\displaystyle \rightleftharpoons }$ 3-methylcatechol + NADH + CO₂

Thus, the two substrates of this enzyme are 1,2-dihydroxy-6-methylcyclohexa-3,5-dienecarboxylate and NAD⁺, whereas its 3 products are 3-methylcatechol, NADH, and CO₂.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 1,2-dihydroxy-6-methylcyclohexa-3,5-dienecarboxylate:NAD+ oxidoreductase (decarboxylating). This enzyme participates in toluene and xylene degradation.

• Higson FK, Focht DD (1992). "Degradation of 2-methylbenzoic acid by Pseudomonas cepacia MB2". Appl. Environ. Microbiol. 58 (1): 194–200. PMC 195191. PMID 1371658.