Involved in the biosynthesis of the coenzyme M (2-mercaptoethanesulfonic acid). Catalyzes the decarboxylation of sulfopyruvate to sulfoacetaldehyde. 3-sulfopyruvate + H(+) = CO2 + sulfoacetaldehyde Binds 1 thiamine pyrophosphate per subunit. Cofactor biosynthesis; coenzyme M biosynthesis; sulfoacetaldehyde from phosphoenolpyruvate and sulfite: step 4/4. Heterododecamer composed of 6 subunits alpha and 6 subunits beta. Cells lacking this gene are partial coenzyme M auxotrophs; they grow poorly in the absence of coenzyme M and retain less than 3% of the wild type level of coenzyme M biosynthesis. Belongs to the TPP enzyme family.