Biosynthesis of tetrahydrofuranyl fatty acids from linoleic acid by clavibacter sp. ALA2

Clavibacter sp. ALA2 converts linoleic acid into many novel oxygenated products including hydroxy FA and tetrahydrofuranyl unsaturated FA (THFA). One of them was tentatively identified by GC‐MS as 12,13,16‐trihydroxy‐9(Z)‐octadecenoic acid (12,13,16‐THOA) (Hou, C.T., H.W. Gardner, and W. Brown, J Am. Oil Chem. Soc. 78∶1167–1169, 2001). We have separated and purified 12,13,16‐THOA from its isomer, 12,13,17‐THOA, by silica gel column chromatography and by preparative TLC. Its structure was then confirmed by proton and 13C NMR analyses. Purified 12,13,16‐THOA was used as a substrate to study the biosynthesis of THFA. Within 24 h of incubation, cells of strain ALA2 converted 12,13,16‐THOA to both 12‐hydroxy‐13,16‐epoxy‐9(Z)‐octadecenoic acid (12‐hydroxy‐THFA) and 7,12‐dihydroxy‐13,16‐epoxy‐9(Z)‐octadecenoic acid (7,12‐dihydroxy‐THFA). The relative abundance of 7,12‐dihydroxy‐THFA increased with incubation time, whereas that of 12,13,16‐THOA and of 12‐hydroxy‐THFA decreased. Therefore, the biosynthetic pathway of THFA from linoleic acid by strain ALA2 is as follows: linoleic acid→12,13‐dihydroxy‐9(Z)‐octadecenoic acid→12,13,16‐THOA→12‐hydroxy‐THEA→7,12‐dihydroxy‐THFA.