Gellerman J L, Schlenk H
Biochim Biophys Acta. 1979 Apr 27;573(1):23-30. doi: 10.1016/0005-2760(79)90169-3.
The lipids of Saprolegnia parasitica contain 5,8,11,14,17-eicosapentaenoic acid as major constituent. No other acid having (n-3) structure was detected, but 5,8,11,14-eicosatetraenoic (arachidonic) acid and its common precursors of (n-6) structure are present in significant amounts. During rapid growth of the organism, [1-14C]acetate was efficiently incorporated into fatty acids. Arachidonic acid was labeled after 2 h to nearly the same extent as any precursor acid and 14C in eicosapentaenoic acid reached this level within 6 h. Results of incubations with labeled fatty acids indicated that, in S. parasitica, oleic, linoleic, (6,9,12)-linolenic and arachidonic acids are major intermediates in the pathway to eicosapentaenoic acid. Methyl-directed desaturation of (n-6) to (n-3) acids does not occur with C18 acids but is specific for the polyunsaturated C20 chain length. Arachidonic acid is the direct precursor of eicosapentaenoic acid.
寄生水霉的脂质中，5,8,11,14,17-二十碳五烯酸是主要成分。未检测到其他具有(n-3)结构的酸，但5,8,11,14-二十碳四烯酸（花生四烯酸）及其常见的(n-6)结构前体大量存在。在该生物体快速生长期间，[1-14C]乙酸盐被有效地掺入脂肪酸中。2小时后，花生四烯酸被标记的程度与任何前体酸几乎相同，二十碳五烯酸中的14C在6小时内达到该水平。用标记脂肪酸进行孵育的结果表明，在寄生水霉中，油酸、亚油酸、(6,9,12)-亚麻酸和花生四烯酸是合成二十碳五烯酸途径中的主要中间体。(n-6)酸到(n-3)酸的甲基定向去饱和作用在C18酸中不会发生，而是特定于多不饱和的C20链长。花生四烯酸是二十碳五烯酸的直接前体。
