title: Oxygen induction of a novel fatty acid n-6 desaturase in the soil protozoon, Acanthamoeba castellanii.
abstract: Induction of fatty acid desaturation is very important for the temperature adaptation of poikilotherms. However, in oxygen-limited late-exponential-phase Acanthamoeba castellanii cultures, oxygen alone was able to induce increased activity of a fatty acid desaturase that converts oleate into linoleate and which has been implicated in the temperature adaptation of this organism. Experiments with Delta(10)-nonadecenoate showed that the enzyme is an n -6 desaturase rather than a Delta(12)-desaturase. It also used preferentially 1-acyl-2-oleoyl-phosphatidylcholine as substrate and NAD(P)H as electron donor. The involvement of cytochrome b (5) as an intermediate electron carrier was shown by difference spectra measurements and anti-(cytochrome b (5)) antibody experiments. Of the three protein components of the desaturase complex, oxygen only increased the activity of the terminal (cyanide-sensitive) protein during n -6 desaturase induction. The induction of this terminal protein paralleled well the increase in overall oleate n -6 desaturation. The ability of oxygen to induce oleate desaturase independently of temperature in this lower eukaryotic animal model is of novel intrinsic interest, as well as being important for the design of future experiments to determine the molecular mechanism of temperature adaptation in poikilotherms.
authors.affiliation: School of Biosciences, Cardiff University, Cardiff CF10 3US, Wales, U.K.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Rutter
authors.forename: Katie L
authors.initials: KL
authors.lastname: Thomas
authors.forename: Derek
authors.initials: D
authors.lastname: Herbert
authors.forename: R James
authors.initials: RJ
authors.lastname: Henderson
authors.forename: David
authors.initials: D
authors.lastname: Lloyd
authors.forename: John L
authors.initials: JL
authors.lastname: Harwood
mesh_terms: D000048:Acanthamoeba / Q000187:drug effects* / Q000201:enzymology; D000818:Animals; D004790:Enzyme Induction / Q000187:drug effects; D044943:Fatty Acid Desaturases / Q000096:biosynthesis*; D010100:Oxygen / Q000494:pharmacology*; D012987:Soil / Q000469:parasitology*
chemical_list: D012987:Soil; D044943:Fatty Acid Desaturases; D010100:Oxygen