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  • Fig D shows that E lagascae VIR


    Fig. 2D shows that E. lagascae VIR E gives two species of radioactive TAG: one represents 45% of total labelled TAG and the smaller more-polar spot (15%) is probably derived from the endogenous 1,2-divernolin instead of the exogenous 1,2-diolein. In this case, the total scintillation counts were greater (411.3) than that recorded (range 15.1–65.6 CPM) for the other TAG spots of the plate (Table 2). Yu et al. (2006) reported that TLC is able to separate TAGs with vernolic acid. Vernonia galamensis (which accumulates vernolic hcv protease inhibitor in the seed oil) DGAT prefers vernoleyl-CoA with divernolin; nevertheless, no selectivity was found in Stokesia laevis (also accumulates vernolic acid) for any acyl receptor. Usually, the literature refers to in vitro assays in which given mixtures of compounds are studied and preferences show up. We speculate that in vivo systems are simpler and could possibly cope with these selectivities up to a point. Yu et al. (2008) report that two DGAT genes isolated from V. galamensis when expressed in yeast have not shown any selectivity towards incorporating vernolic acid into TAGs. Microsomes of E. lathyris showed more preference for diolein (the native DAG of the species) than those of E. lagascae (Fig. 3): an increase of 53% of labelled TAG against 2%. According to He et al. (2005), it is difficult to study substrate specificities of DGATs using microsomal fractions from developing seeds since there are a number of activities present. Using a yeast cell system, they proved that R. communis DGAT clearly showed a preference for diricinolein against diolein at 0.25mM. McKeon et al. (2005) suggested that combined effects of enzymes’ preferences are responsible for the production of oil with a unique composition. DAGs are common precursors for membrane lipids and for TAGs. The acyl-CoA pool is sampled by three acyltransferases, which transfer the acyl groups successively to the 1, 2, and 3 carbons of glycerol to form a TAG. DGAT enzyme is unique to cells that are actively synthesizing storage oils, for example the embryos or the endosperms of oilseeds; this is important to remove and store the unusual fatty acids that could be toxic for the lipid membranes (Millar et al., 2000). The preparations from the three euphorbs (R. communis, E. lagascae and E. lathyris) were able to use common (to both membrane and storage lipids) acyl donors (oleoyl-CoA) and receptors (diolein), possibly suggesting that DGAT enzymes would not be a limiting factor (even if they show some preferences) to engineer Euphorbiaceae crops with functionalized fatty acids. This means that for instance castor or E. lagascae could be suitable species to be bred for producing in large amounts a range of fatty acids for industrial use. Also that the euphorb DGAT genes could be used for plant transformations to produce greater accumulations of unusual fatty acids in TAG (that have not been successful so far). Settlage et al. (1998) reported that genotypic differences in DGAT activity are related to genetic variations in oil content among soybean. Hydroxylated fatty acids such as ricinoleate (C18:1-OH) are important oleochemicals since they allow many chemical conversions to be carried out. Lesquerolic acid (C20:1-OH), synthesized by Lesquerella fendleri (Brassicaceae), is considered a new domestic raw material in the United States, which does not cause toxicity and allergenic reactions as castor beans. Epoxydized fatty acids such as vernoleate, present in E. lagascae or Vernonia species (Compositae), are functional fatty acids with similar polarity (to hydroxy-) but with potential new applications. The skin irritant properties of Euphorbia latex is a drawback for cultivation but the fact that euphorbs are non-food species, very diverse in seed fatty acid composition and why not? more plastic for genetic manipulations are positive aspects to be taken into account.
    Introduction Triglycerides (TG), the most leading storage form of energy in eukaryotic cells and essential for normal physiology. However, excess accumulation of TG in tissue can lead to a variety of disorders, such as obesity, insulin resistance and hepatic steatosis [1]. For these reasons, inhibition of TG synthesis has been considered as an efficient strategy for treatment of obesity and type II diabetes [2]. Diacylglycerol acyltransferase (DGAT) catalyzes the acyl residue transfer from acyl-CoA to diacylglycerol (DAG), which the exclusive key enzyme for the final step in TG synthesis [3]. Molecular studies showed: DGAT enzymes are encoded by two non-homology genes: DGAT1 and DGAT2, and both genes are ubiquitously expressed [4]. Meanwhile, DGAT1 as a member of the acyl CoA: cholesterol acyltransferase (ACAT) gene family is more homologous with ACAT1 and ACAT2 than with DGAT2, which is more closely related to the monoacylglycerol acyl transferase (MGAT) enzymes [5]. Recent studies have shown that: mice knockout DGAT1 has provided an understanding of the relationship between TG synthesis and metabolic syndrome like obesity and type II diabetes. These DGAT1 deficient mice were resistant to weight gain when fed a high-fat diet through mechanisms that involved improve energy expenditure and increased sensitivity in insulin and leptin [6]. Based on these aspects, searching for novel, selective, and orally bio-available DGAT1 inhibitors for the treatment of obesity and type II diabetes have been intensified.