Identification of a functional DddX-like enzyme that catalyzes dimethylsulfoniopropionate cleavage in marine bacteria

Dimethylsulfoniopropionate (DMSP), a ubiquitous organosulfur compound in marine environments, plays an important role in global sulfur cycling and climate regulation. Many marine microorganisms catabolize DMSP through DMSP lytic enzymes, producing the infochemical and potential climate-cooling gas dimethyl sulfide (DMS). The marine Roseobacter group (MRG) is one of the most abundant heterotrophic bacteria groups in marine ecosystems and an active participant in DMSP cycling. To expand our knowledge of the diversity of DMSP lytic enzymes, we identified and characterized a functional DddX-like enzyme from the MRG strain Neptunicoccus cionae H-12 and other related bacteria, such as Leisingera spp., Sulfitobacter spp., and Roseovarius spp. This enzyme catalyzes the cleavage of DMSP into DMS and acryloyl-CoA. Although the DddX-like enzyme belongs to the same acyl-CoA synthetase superfamily as DddX, a previously reported DMSP lytic enzyme, it shares low amino acid sequence identity (∼23%) with DddX. Phylogenetic analysis suggested that the DddX-like enzyme formed a separate clade from DddX, with the DddX-like enzyme predominantly distributed in the cosmopolitan MRG. Bioinformatic analysis indicated that the relative abundance of dddX and dddX-like genes, along with their transcripts, is notably high in marine environments, suggesting their important roles in DMSP cycling. Our findings enhance knowledge of DMSP lytic enzymes and provide novel insights into global sulfur cycling processes.