Enantioselective oxidation of thiafatty acids by an algal Δ12-desaturase

The whole-cell Chlorella vulgaris (211/8 K) system allows us to use thiastearate methyl esters as a mechanistic probe of the Δ12-desaturation process. The 6-, 7-, 12- and 13-thiastearates are converted intracellularly to the corresponding Δ9-desaturated products, which can then be processed by the Δ12-desaturase. The 6- and 7-thiaoleoyl are then desaturated respectively to the 6- and 7-thialinoleoyl products; the 12- and 13-thiaoleates are oxidised to the corresponding sulfoxides with a high enantioselectivity (ee≥90%), confirming the oxygenase activity of the Δ12-desaturase with appropriately modified substrates.