Abstract
Dimethylsulfoniopropionate (DMSP) is an abundant and ubiquitous organosulfur molecule in marine environments with important roles in global sulfur and nutrient cycling. Diverse DMSP lyases in some algae, bacteria, and fungi cleave DMSP to yield gaseous dimethyl sulfide (DMS), an infochemical with important roles in atmospheric chemistry. Here, we identified a novel ATP-dependent DMSP lyase, DddX. DddX belongs to the acyl-CoA synthetase superfamily and is distinct from the eight other known DMSP lyases. DddX catalyses the conversion of DMSP to DMS via a two-step reaction: the ligation of DMSP with CoA to form the intermediate DMSP-CoA, which is then cleaved to DMS and acryloyl-CoA. The novel catalytic mechanism was elucidated by structural and biochemical analyses. DddX is found in several Alphaproteobacteria, Gammaproteobacteria, and Firmicutes, suggesting that this new DMSP lyase may play an overlooked role in DMSP/DMS cycles.
Highlights
The organosulfur molecule dimethylsulfoniopropionate (DMSP) is produced in 42 massive amounts by many marine phytoplankton, macroalgae, angiosperms, bacteria and animals (Curson et al, 2018; Stefels, 2000; Otte et al, 2004; Curson et al, 2017; Raina et al, 2013)
DMSP is oxidized to dimethylsulfoxonium propionate (DMSOP), which is further metabolized to dimethylsulfoxide (DMSO) and acrylate; enzymes involved in this pathway are unknown (Thume et al, 2018) (Figure 1)
Gas chromatography (GC) analysis showed that Psychrobacter sp
Summary
The organosulfur molecule dimethylsulfoniopropionate (DMSP) is produced in 42 massive amounts by many marine phytoplankton, macroalgae, angiosperms, bacteria and animals (Curson et al, 2018; Stefels, 2000; Otte et al, 2004; Curson et al, 2017; Raina et al, 2013). Bacteria can metabolize DMSP via three known pathways, the demethylation pathway (Howard et al, 2006), the recently reported oxidation pathway (Thume et al, 59 2018), and the lysis pathway (Curson et al, 2011b) (Figure 1). Diverse lyases cleave DMSP to produce DMS and acrylate or 3-hydroxypropionate-CoA (3-HP-CoA), which are further metabolized by ancillary enzymes (Curson et al, 2011b; Johnston et al, 2016) (Figure 1). There is large biodiversity in DMSP lysis, with eight different known DMSP lyases that encompass four distinct protein families (DddD a CoA-transferase; DddP a metallopeptidase; cupin containing DddL, DddQ, DddW, DddK and DddY; and Alma[1] an aspartate racemase) functioning in diverse marine bacteria, algae and fungi (Figure 1) (Curson et al, 2011b; Johnston et al, 2016). Several bacterial isolates were reported to produce DMS from DMSP but lack known DMSP lyases in their genomes (Liu et al, 2018; Zhang et al, 2019), suggesting the presence of novel enzyme(s) for DMSP degradation in nature
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