Purification and characterization of L-methionine decarboxylase from Crypthecodinium cohnii

L-Methionine decarboxylase [EC 4.1.1.57] was purified from the marine dinoflagellate Crypthecodinium cohnii. After four purification steps including anion exchange chromatography and size-exclusion chromatography, the enzyme was purified 215-fold and the yield was 0.1%. The purified enzyme showed a single protein band on polyacrylamide gel electrophoresis. The molecular weight of the enzyme estimated by gel filtration was 204,000. The optimum pH and temperature of the enzyme activity were 7.3 and 30 degrees C, respectively. The enzyme activity was stimulated by the addition of pyridoxal phosphate (PLP) and was inhibited by the typical inhibitors of PLP dependent enzymes. The decarboxylated product of L-methionine by the enzyme was 3-methylthiopropanamine (MTPA). The enzyme should be the key enzyme in dimethylsulfoniopropionate (DMSP) biosynthesis from L-methionine in C. cohnii. This shows that C. cohnii has the DMSP biosynthetic pathway from L-methionine to DMSP via MTPA.