Dimethyl sulfide (DMS)-producing enzyme (PubMed:17272727, PubMed:25140443). Acts both as a transferase and a lyase: uses acetyl-coenzyme A (acetyl-coA) and dimethylsulfonioproprionate (DMSP) as substrates to produce DMS, acetate and 3-hydroxypropionate-CoA (3HP-CoA). Mediates the CoA-transferase prior to lyase activity (PubMed:25140443). DMS is the principal form by which sulfur is transported from oceans to the atmosphere and is a key component of the ocean sulfur cycle (PubMed:17272727, PubMed:25140443). kcat is 10.8 sec(-1). Cells are unable to grow on dimethylsulfonioproprionate (DMSP) as sole carbon source. At least 10 million metric tons of volatile dimethyl sulfide (DMS) are released into the atmosphere annually by the dimethylsulfonioproprionate lyase in oceans. It is a component of the tangy aroma of the seaside and functions as a chemical attractant that guides various marine animals, such as sea birds, invertebrates, and some mammals, toward potential food supplies. DMS oxidation products act as condensation nuclei, causing water molecules to coalesce, with possible effects on local climate through enhanced cloud formation. Belongs to the CoA-transferase III family.