Ref ID : 4341
A. Lesley Jones, Nancy L. Pruitt, David Lloyd, and John L. Harwood; Temperature-induced Changes in the Synthesis of Unsaturated Fatty Acids by Acanthamoeba castellanii. J.Protozool. 38(6):532-536, 1991
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Major fatty acid components of Acanthamoeba castellanii lipids extracted after growth at 30 degrees C include myristate, palmitate, stearate and the polyunsaturates linoleate, eicosadienoate, eicosatrienoate and arachidonate, with oleate as the sole major monounsaturated fatty acid. By comparison, growth at 15 degrees C gave increased linoleate, eicosatrienoate and arachidonate, but decreased oleate and palmitate. When the growth temperature was shifted downwards from 30 degrees C to 15 degrees C, increased lipid unsaturation occurred over period of 24 hr; thus decreases of oleate and eicosadienoate were accompanied by increases in linoleate, eicosatrienoate, arachidonate and eicosapentaenoate. An upwards shift from 15 degrees C to 30 degrees C gave negligible alterations in fatty acid composition over a similar period. At 15 degrees C organisms rapidly use [1-14C]acetate for de novo fatty acid synthesis; stearate is converted via oleate to further desaturation and chain elongation products. Similar short term experiments at 30 degrees C indicate only de novo synthesis and delta9-desaturation; synthesis of polyunsaturates was a much slower process. Rapid incorporation of [1-14C]oleate at 30 degrees C was not accompanied by metabolic conversion over two hours, whereas at 15 degrees C n-6 desaturation to linoleate was observed. Temperature shift of organisms from 15 degrees C to 30 degrees C in the presence of [1-14C]acetate revealed that over half of the fatty acids in newly-synthesised lipids were saturated, but the proportions of unsaturated fatty acids increased with time until the total polyenoate components reached 17% after 22 hr. A shift of temperature in the reverse direction gave a corresponding figure of 60% for polyunsaturated fatty acids. These results emphasize the importance of n-6 desaturation in the low temperature adaptation of Acanthamoeba castellanii.