A multifunctional enzyme complex composed of five different polypeptides that catalyzes the decarbonylation of acetyl-CoA, cleaves the C-C and C-S bonds in the acetyl moiety of acetyl-CoA, oxidizes the carbonyl group to CO2 and transfers the methyl group to tetrahydrosarcinapterin. These reactions are important for methanogenesis. [ http://www.ncbi.nlm.nih.gov/pubmed/11607176 http://www.ncbi.nlm.nih.gov/pubmed/7693685 GOC:mengo_curators http://www.ncbi.nlm.nih.gov/pubmed/8955306 ]