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A phosphopantetheinyl transferase (PPTase) gene (pfaE), cloned from the docosahexaenoic acid (DHA)-producing bacterium Moritella marina strain MP-1, has an open reading frame of 861 bp encoding a 287-amino acid protein. When the pfaE gene was expressed with pfaA-D, which are four out of five essential genes for biosynthesis of eicosapentaenoic acid (EPA) derived from Shewanella pneumatophori SCRC-2738 in Escherichia coli, the recombinant produced 12% EPA of total fatty acids. This suggests that pfaE encodes a PPTase required for producing n À 3 polyunsaturated fatty acids, which is probably involved in the synthesis of DHA in M. marina strain MP-1.

The nutritional and pharmaceutical values of long-chain polyunsaturated fatty acids (LC-PUFAs) such as arachidonic, eicosapentaenoic and docosahexaenoic acids have been well recognized. These LC-PUFAs are physiologically important compounds in bacteria and eukaryotes. Although little is known about the biosynthetic mechanisms and functions of LC-PUFAs in bacteria compared to those in higher organisms, a combination of genetic, bioinformatic, and molecular biological approaches to LC-PUFA-producing bacteria and some eukaryotes have revealed the notably diverse organization of the pfa genes encoding a polyunsaturated fatty acid synthase complex (PUFA synthase), the LC-PUFA biosynthetic processes, and tertiary structures of the domains of this enzyme. In bacteria, LC-PUFAs appear to take part in specific functions facilitating individual membrane proteins rather than in the adjustment of the physical fluidity of the whole cell membrane. Very long chain polyunsaturated hydrocarbons (LC-HCs) such as hentriacontanonaene are considered to be closely related to LC-PUFAs in their biosynthesis and function. The possible role of LC-HCs in strictly anaerobic bacteria under aerobic and anaerobic environments and the evolutionary relationships of anaerobic and aerobic bacteria carrying pfa-like genes are also discussed.

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The colony-forming ability of Escherichia coli genetically engineered to produce eicosapentaenoic acid (EPA) grown in 3 mM hydrogen peroxide (H 2 O 2 ) was similar to that of untreated cells. It was rapidly lost in the absence of EPA. H 2 O 2 -induced protein carbonylation was enhanced in cells lacking EPA. The fatty acid composition of the transformants was unaffected by H 2 O 2 treatment, but the amount of fatty acids decreased in cultures of cells lacking EPA and increased in cultures of cells producing EPA, suggesting that cellular EPA is stable in the presence of H 2 O 2 in vivo and may protect cells directly against oxidative damage. We discuss the possible role of EPA in partially blocking the penetration of H 2 O 2 into cells through membranes containing EPA.