Involved in the biosynthesis of the coenzyme M (2-mercaptoethanesulfonic acid). Catalyzes the decarboxylation of sulfopyruvate to sulfoacetaldehyde. 3-sulfopyruvate + H(+) = CO2 + sulfoacetaldehyde Cofactor biosynthesis; coenzyme M biosynthesis; sulfoacetaldehyde from phosphoenolpyruvate and sulfite: step 4/4. Heterododecamer composed of 6 subunits alpha and 6 subunits beta. Belongs to the ComD family.