Isolation and characterization of a gene encoding a S-adenosyl-l-methionine-dependent halide/thiol methyltransferase (HTMT) from the marine diatom Phaeodactylum tricornutum: Biogenic mechanism of CH3I emissions in oceans

► Marine microalgae including Phaeodactylum tricornutum emit methyl halides. ► These strains exhibit SAM: halide/thiol methyltransferase (HTMT) activity. ► CH3I emission increases in response to iodide (I−) concentration in the media. ► A gene encoding HTMT was isolated from P. tricornutum, expressed, and characterized. ► Considering the kcat/Km, it was concluded that the enzyme is specific for I−.