Catalyzes the conversion 3-sulfinopropanoyl-CoA (3SP-CoA) to propanoyl-CoA by abstraction of sulfite (PubMed:23354747, PubMed:26057676). Does not show dehydrogenase activity (PubMed:23354747). Involved in the degradation of 3,3'-dithiodipropionate (DTDP), a sulfur-containing precursor substrate for biosynthesis of polythioesters (PTEs) (PubMed:23354747). 3-sulfinopropanoyl-CoA + H2O = H(+) + propanoyl-CoA + sulfite Binds 1 FAD per subunit. kcat is 3.13 sec(-1). Homotetramer. Deletion of the gene completely impairs growth on DTDP or 3-sulfinopropanoyl (3SP) as the sole carbon source. Does not catalyze the dehydrogenation of acyl-CoA thioesters (PubMed:23354747). The absence of dehydrogenase activity is most probably caused by the absence of a catalytic glutamate residue in either of the two positions conserved throughout the acyl-CoA dehydrogenase family (PubMed:23354747). Belongs to the acyl-CoA dehydrogenase family.