Identification and Expression of a Rat Fatty Acid Elongase Involved in the Biosynthesis of C18 Fatty Acids

Abstract

A major part of the palmitic acid (C16:0) generated by fatty acid synthase is converted into stearic acid (C18:0) via carbon chain elongation. Here, we describe the cloning and expression of a rat hepatic enzyme, rELO2, responsible for the elongation of C16:0, presumably at the condensing reaction. Heterologous expression experiments in a yeast, Saccharomyces cerevisiae, demonstrated the elongation activity of rELO2 on C16:0 and to a lesser extent, C18:0 and fatty acids with low desaturation degree. This was distinct from that rELO1, a rat homolog of HELO1, which preferably catalyzed the elongation of mono-and polyunsaturated fatty acids of C16-C20. The Northern analysis showed that the expression of rELO2, but not rELO1, in hepatocytes was activated by the cycles of fasting and refeeding rats on a fat-free diet. Under these conditions, the rELO1 was expressed constitutively in various tissues but the rELO2 transcripts were detected predominantly in liver.

ELOVL2 overexpression enhances triacylglycerol synthesis in 3T3‐L1 and F442A cells

“…An abundant amount of Elovl2 mRNA in testis suggested that ELOVL2 elongates PUFAs [8]. This was subsequently demonstrated in mouse [10], human [29] and rat [30,31] orthologs, and in this study (Fig. 1C).…”

Zebrafish cDNA Encoding Multifunctional Fatty Acid Elongase Involved in Production of Eicosapentaenoic (20:5n-3) and Docosahexaenoic (22:6n-3) Acids

“…The zebrafish enzyme also had substantial C 20 PUFA elongase activity, converting some 46% and 26% of 20:5n-3 and 20:4n-6, respectively, to the respective C 22 products. This is similar to human (ELOVL5) and rat elongases (rELO1), which also have high activity on 20:5n-3 and 20:4n-6 (Leonard et al, 2000b: Inagaki et al, 2002, but in contrast to the elongases of M. alpina and C. elegans which show virtually no activity towards C 20 PUFA (Parker-Barnes et al, 2000;Beaudoin et al, 2000). However, in contrast to the previously reported human and rat elongases described above, the zebrafish elongase also displayed the capacity to elongate C 22 PUFA, converting about 5% of 22:5n-3 to 24:5n-3 in the recombinant yeast system studied.…”

“…Functional characterisation has previously been reported for PUFA elongases of nematode (C. elegans), fungus, (M. alpina), rat and human with all four enzymes being predominantly active on C 18 PUFA (Beaudoin et al, 2000;Leonard et al, 2000b;Parker-Barnes et al, 2000;Inagaki et al 2002). This was also the case with zebrafish elongase, the enzyme achieving 90% conversion of 18:4n-3 substrate and 60% of 18:3n-6.…”

Physiological roles of fatty acyl desaturases and elongases in marine fish: Characterisation of cDNAs of fatty acyl Δ6 desaturase and elovl5 elongase of cobia (Rachycentron canadum)

“…Nearly all the other cloned and functionally characterised elongases from fish reported so far show sequences and functionality similar to mammalian ELOVL5 elongases (Hastings et al, 2005;Agaba et al, 2004Agaba et al, , 2005. The fish Elovl5s have a wider substrate specificity than mammalian ELOVL5s, which elongate predominantly C18 and, to a lesser extent, C20 fatty acids but not C22, whereas most fish Elovl5-like elongases can also elongate 22:5n-3 to 24:5n-3, albeit at a very low level (Leonard et al, 2000;Inagaki et al, 2002;Agaba et al, 2005). Thus, theoretically only this one Elovl5-like elongase might be required for the production of DHA from 18:3n-3 in freshwater fish and, in marine fish, this one elongase would be all that is required to perform both the elongations of EPA necessary for the production of DHA.…”