Purification and characterization of dimethylsulfoniopropionate lyase from an alcaligenes-like dimethyl sulfide-producing marine isolate

Abstract

Dimethyl sulfide (DMS) is quantitatively the most important biogenic sulfur compound emitted from oceans and salt marshes. It is formed primarily by the action of dimethylsulfoniopropionate (DMSP) lyase which cleaves DMSP, an algal osmolyte, to equimolar amounts of DMS and acrylate. This report is the first to describe the isolation and purification of DMSP lyase. The soluble enzyme was purified to electrophoretic homogeneity from a facultatively anaerobic gram-negative rod-shaped marine bacterium identified as an Alcaligenes species by the Vitek gram-negative identification method. The key to successful purification of the enzyme was its binding to, and hydrophobic chromatography on, a phenyl-Sepharose CL-4B column. DMSP lyase biosynthesis was induced by its substrate, DMSP; its product, acrylate; and also by acrylamide. The relative effectivenesses of the inducers were 100, 90, and 204%, respectively. DMSP lyase is a 48-kDa monomer with a Michaelis-Menten constant (K m) for DMSP of 1.4 mM and a V max of 408 mol/min/mg of protein. It converted DMSP to DMS and acrylate stoichiometrically. The similar K m values measured for pure DMSP lyase and the axenic culture, seawater, and surface marsh sediment suggest that the microbes in these ecosystems must have enzymes similar to the one purified from our marine isolate. Anoxic sediment populations, however, have a 40-fold-lower K m for this enzyme (30 M), possibly giving them the capability to metabolize much lower levels of DMSP than the aerobes.

Grazing‐activated production of dimethyl sulfide (DMS) by two clones of Emiliania huxleyi

“…Two E. huxleyi blooms might show very different temporal patterns of DMS production. Second, our work reinforces the diverse nature of DMS formation, because grazing-activated prey production of DMS must now be added to other known DMS production mechanisms, including production by growthactive phytoplankton DMSP lyases as in P. pouchetii (Stefels and van Boekel 1993), inducible bacterial DMSP lyases (de Souza and Yoch 1995), and heterotroph (Ishida 1968) or predator-associated (Dacey et al 1994) DMSP lyases.…”

“…Clone 373 cells grown in high-nitrate (883 PM) and low-nitrate (50 PM) f/2 showed similar in vitro rates (data not shown). Neither enzyme exhibited any lytic ability with the closely related sulfonium compound, dimethylsulfonioacetate (DMSA), similar to a DMSP lyase isolated from a marine bacterium (de Souza and Yoch 1995). However, cell-free extracts of either enzyme failed to cross-react by western blot or ELBA with a polyclonal antibody prepared against Production of DMS from dissolved DMSP by whole and Zysed cells-When exponentially growing cells were concentrated by centrifugation and gently resuspended into fresh f/2 medium, no DMS production from endogenous DMSP was observed in short-term incubations, as shown for clone 373 (Fig.…”

Ecological significance of compatible solute accumulation by micro-organisms: from single cells to global climate

“…The tertiary sulfonium compound DMSP, which is synthesised as a compatible solute by micro-algae, macro-algae and some aquatic angiosperms, is also metabolised as a carbon source by a metabolically diverse range of heterotrophic bacteria, in both the water column and sediments [149,150,175,176]. In addition DMS an intermediate in the catabolism of DMSP can be utilised as an electron donor for photosynthesis by some anaerobic phototrophic bacteria [187,188] and the dimethyl sulfoxide (DMSO) generated during this photo-oxidation can subsequently be reduced back to DMS, by facultatively and strictly anaerobic bacteria, including sulfate reducing bacteria [1891 91].…”

“…DMSP is synthesised as a compatible solute by many micro-and macro-algae, and aquatic angiosperms [17,132,212^214]. DMSP released to the environment can be rapidly converted to DMS by DMSP-lyases produced by the plants themselves or the associated bacterial £ora [134,149,150,215]. This DMS may either £ux to the atmosphere, be further metabolised by bacteria [190,216] or be biologically or photochemically oxidised to dimethylsulfoxide (DMSO) [187,188,217].…”

“…cycle DMS £uxes to the atmosphere arise due to the lysis of the compatible solute DMSP in the water column by DMSP-lysases produced by the micro-algae and/or the bloom associated bacterial community [134,149,150,215,266,267]. However, dissolved DMSP is also metabolised directly by bacteria via a demethylation/demethiola-tion pathway (see Fig.…”