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. Inhibited by oxygen when heated in air at 80 degrees Celsius. The enzyme is reactivated by addition of dithionite. 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 TPP enzyme family. The sequence corresponding to this entry was originally entered in Swiss-Prot as AC Q57704 in November 1997 and was deleted in July 1999 because TIGR removed the CDS for that ORF. We have recreated it because of the evidence (PubMed:10940029) that it really exists.