The biosynthesis of omega-3 in deep-sea bacteria takes place not by the desaturation and elongation of saturated fatty acids, but rather by a polyunsaturated fatty acid (PUFA) synthase system which resembles a PKS in that it builds the fatty acid one acyl unit at a time, introducing the double bonds as the chain grows attached to an acyl carrier protein (35).
The role of tandem acyl carrier protein domains in polyunsaturated fatty acid biosynthesis.
Abbreviations: EST, expressed sequence tag; FAD, fatty acid desaturase; RT-PCR, reverse transcription-polymerase chain reaction; SACPD, stearoyl acyl carrier protein
The fatty acids produced through this process are palmitic (16:0), stearic (18:0), and oleic (18:1[delta]9) acids, which are released from acyl carrier protein
by the activities of thioesterases.
Until now, the following signature sequences could be observed: acyl carrier proteins
, (ED)LGXDSL(DAT); ArCPs, (DN)LXXXGLDSXR ; PCPs preceding a C or Te domain, DXFFXXLGGHSLK; PCPs preceding an epimerization domain, DXFFXXLGGDSIK; and C- terminal PCPs, FF(ED)XGGNSLK.