title: De novo arachidonic acid synthesis in Perkinsus marinus, a protozoan parasite of the eastern oyster Crassostrea virginica.
abstract: The capability of synthesizing fatty acids de novo in the meront stage of the oyster protozoan parasite, Perkinsus marinus, was investigated employing stable-isotope-labeled precursors (1,2 13C-acetate and palmitic-d(31) acid). Fatty acid methyl esters derived from 1,2 13C-acetate and palmitic-d(31) acid were analyzed using gas chromatography/mass spectrometry and gas chromatography/flame ionization detection. Results revealed that in vitro cultured P. marinus meronts utilized 13C-acetate to synthesize a range of saturated and unsaturated fatty acids. The saturated fatty acids 14:0, 16:0, 18:0, 20:0, 22:0, 24:0 and the unsaturated fatty acids, 18:1(n-9), 18:2(n-6), 20:1(n-9), 20:2(n-6), 20:2(n-9), 20:3(n-6), 20:4(n-6) were found to contain 13C, after 7, 14, and 21 days incubation with the precursor. This indicates that meronts can synthesize fatty acid de novo using acetate as a substrate. Meronts efficiently elongated 16:0-d(31) to 18:0, 20:0, 22:0, 24:0, but desaturation activity was limited, after 7 and 14 days cultivation. Only a small quantity of 18:1-d(29) was detected. This suggests that meronts cannot directly convert exogenous palmitic acid or its products of elongation to unsaturated counterparts. The ability to synthesize 20:4(n-6) from acetate is particularly interesting. No parasitic protozoan has been reported to be capable of synthesizing long chain essential fatty acids, such as 20:4(n-6) de novo. Future study will be directed to determine whether the observed in vitro activities indeed reflect the in vivo activities, when meronts are associated with the host.
authors.affiliation: Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA. chu@vims.edu
authors.forename: Fu-Lin E
authors.initials: FL
authors.lastname: Chu
authors.forename: Eric
authors.initials: E
authors.lastname: Lund
authors.forename: Philippe
authors.initials: P
authors.lastname: Soudant
authors.forename: Ellen
authors.initials: E
authors.lastname: Harvey
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000032:analysis / Q000096:biosynthesis*; D002247:Carbon Isotopes; D002849:Chromatography, Gas; D056890:Eukaryota / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D010125:Ostreidae / Q000469:parasitology*; D019308:Palmitic Acid / Q000378:metabolism; D013997:Time Factors
chemical_list: D002247:Carbon Isotopes; D005227:Fatty Acids; D016718:Arachidonic Acid; D019308:Palmitic Acid