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.
