Dimethylsulfoniopropionate

  Dimethylsulfoniopropionate ((CH₃)₂S⁺CH₂CH₂COO⁻; more frequently abbreviated to DMSP), is a metabolite found in marine phytoplankton, seaweeds and some species of terrestrial and aquatic vascular plants. Older scientific literature refers to it as dimethyl-β-propiothetin. Although originally considered to act only as an osmolyte, several other physiological and environmental roles have also been discovered.

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DMSP is broken down by marine microbes to form two major volatile sulfur products, each with distinct effects on the environment. It's major breakdown product is methanethiol (CH₃SH) which is assimilated by bacteria into protein sulfur.

Its second volatile breakdown product is dimethyl sulfide (CH₃SCH₃; DMS). Most DMS in seawater is cleaved from DMSP by the enzyme DMSP lyase, although many non-marine species of bacteria convert methanethiol to DMS.

DMS is also taken up by marine bacteria, but not as rapidly as methanethiol. Although DMS usually consists of less than 25% of the volatile breakdown products of DMSP, the high reactivity of methanethiol makes the steady-state DMS concentrations in seawater approximately 10 times those of methanethiol (~3 nM vs. ~0.3 nM). Curiously, there have never been any published correlations between the concentrations of DMS and methanethiol. This is probably due to the non-linear abiotic and microbial uptake of methanethiol in seawater, and the comparatively low reactivity of DMS. However, a significant portion of DMS in seawater is oxidized to dimethyl sulfoxide (DMSO).

There is a considerable interest in DMS in the scientific literature that focuses on global climate. DMS is thought to play a role in the earth's heat budget by decreasing the amount of solar radiation that reaches the earth's surface.

DMSP has also been implicated in influencing the taste and odour characteristics of various products. For example, although DMSP is odour- and tasteless, it is accumulated at high levels in some marine herbivores or filter feeders when feeding on diets with a high DMSP content. Increased growth rates, vigour and stress resistance among animals cultivated on such diets have been reported in the scientific literature. However, the volatile breakdown product of DMSP, DMS, is responsible for repellent, ‘off’ tastes and odours that develop in some seafood products after death because of the action of bacterial DMSP-lyase and during processing because of the thermal decomposition of DMSP into DMS and acrylate.

See also

• CLAW hypothesis