Involved in the assimilation of dimethylsulphoniopropionate (DMSP), an important compound in the fixation of carbon in marine phytoplankton, by catalyzing both the hydration and the hydrolysis of 3-(methylthio)acryloyl-CoA (MTA-CoA) to acetaldehyde, CO2, MeSH, and CoA (PubMed:21562561, PubMed:23704947). 3-(methylsulfanyl)acryloyl-CoA + 2 H2O = acetaldehyde + CO2 + CoA + methanethiol kcat is 44 sec(-1) for 3-(methylthio)acryloyl-CoA (for CoA ester hydrolysis). kcat is 0.9 sec(-1) for 3-(methylthio)propanoyl-CoA (for CoA ester hydrolysis). kcat is 13.2 sec(-1) for 3-hydroxybutyryl-CoA (for CoA ester hydrolysis). kcat is 47 sec(-1) for 3-(methylthio)acryloyl-CoA (for MeSH release). kcat is 42 sec(-1) for crotonyl-CoA (for hydration). Homohexamer; dimer of trimers. Cells lacking this gene do not grow on methylmercaptopropionate (MMPA) as the sole source of carbon. Growth is severely inhibited on dimethylsulphoniopropionate (DMSP). Belongs to the enoyl-CoA hydratase/isomerase family.