ENZYMATIC CLEAVAGE OF DIMETHYLSULFONIOPROPIONATE (DMSP) IN CELL-FREE-EXTRACTS OF THE MARINE MACROALGA ENTEROMORPHA-CLATHRATA (ROTH) GREV, (ULVALES, CHLOROPHYTA)

The enzymatic cleavage of dimethylsulfoniopropionate (DMSP) to dimethy lsulfide (DMS) in the marine macroalga Enteromorpha clathrata (Roth) G rev. (Ulvales, Chlorophyta) showed a maximum activity of 3.1 mu mol DM S min(-1) (mg protein)(-1) at 25 degrees C and a pH optimum of 6.2 to 6.4. The activity was more sensitive to temperature than to pH changes . With ammonium sulfate precipitation, approximately 90% of the activi ty was found in the 0-35% fraction, indicating a fairly hydrophobic en zyme. Activity was increased by addition of detergents during extracti on. These results suggest that the DMSP lyase enzyme is probably membr ane-bound in vivo. The enzyme activity is relatively insensitive to ch loride salt concentrations. Addition of nucleosides and nucleotides di d not increase enzyme activity. After hyperosmotic shock for 72 h, enz yme activity increased 1.7-fold and intracellular DMSP concentration w as enhanced from initially 80 mmol DMSP (kg freshweight)(-1) to 107 mm ol DMSP (kg freshweight)(-1). The results suggest that DMSP cleavage w ithin the cell by algal DMSP lyase may contribute to the production of oceanic and atmospheric DMS.