Abstract
In 1996, genes involved in the biosynthesis of a long-chain polyunsaturated fatty acid (LCPUFA), eicosapentaenoic acid (EPA), were first cloned from a bacterium isolated from the intestines of marine fish. This was approximately 10 years after the discovery of deep-sea psychrophilic bacteria capable of producing EPA and docosahexaenoic acid (DHA). Homologous genes now designated as pfa genes, including those responsible for the biosynthesis of DHA have been found in marine bacteria. These pfa genes generally consisted of five pfaA−pfaE genes encoding multifunctional proteins and were similar to those required for polyketide biosynthesis. The recombinant production of EPA and DHA mostly in Escherichia coli has been achieved. Although comparable pfa genes sequences can be retrieved from DNA databases, including those established using bacteria not only from cold temperature environment but also from subtropical and tropical regions, the distribution of typical pfa genes responsible for LCPUFA biosynthesis was restricted in some genera of marine γ-proteobacteria. Recent studies demonstrated that pfa genes, together with four oleA−oleD genes, were involved in the biosynthesis of a very long-chain polyunsaturated hydrocarbon, hentriacontanonaene (C31:9). Interestingly a set of pfa and ole genes was presumed to be distributed in all LCPUFA-producing bacteria and even in some strictly anaerobic bacteria that contain C31:9. This review describes the structure of bacterial pfa genes responsible for the biosynthesis of EPA and DHA, and their distribution in marine bacterial lineages and possible usage for practical production of LCPUFAs.
