DMSP lyase in marine macro- and microalgae: interspecific differences in cleavage activity

The enzymatic cleavage of dimethylsulfoniopropionate (DMSP) to dimethylsulfide (DMS) was investigated in twenty-one strains of marine macro- and microalgae, representing seven algal classes. The enzymes involved in this cleavage are DMSP lyases, producing DMS from DMSP. All algal strains tested were able to synthesize and accumulate various levels of intracellular DMSP but only twelve strains showed DMSP lyase activity. It was possible to identify subgroups of strong and weak DMS producers. The first subgroup included three Enteromorpha species (E. clathrata, E. intestinalis, E. compressa) and Phaeocystis sp. with specific activities in crude cell extracts ranging from 7 to over 100 nmol DMS min-1 (mg cell protein)-1. The second subgroup was composed of a sub-antarctic strain of Acrosiphonia arcta, Polysiphonia lanosa, two strains of Emiliania huxleyi, Acrosiphonia sonderi, Ulva lactuca and Enteromorpha bulbosa. In this subgroup activity ranged from 0.01 to 0.2 nmol DMS min-1 (mg cell protein)-1. No DMSP lyase was detectable in a sub-arctic strain of Acrosiphonia arcta, Acrosiphonia sonderi, Monostroma arcticum, Prasiola crispa, Polysiphonia urceolata, Ascoseira mirabilis, Laminaria saccharina and Tetraselmis subcordiformis. Non-optimal assay conditions and bacterial contamination may have affected rates in some samples, but the results suggest the widespread presence of DMSP lyase among algal taxa, and also raises the possibility that closely-related species may have quite different lyase activities or function.