Fatty acid Δ5 desaturation in rat liver cell nuclei
- Cite this article as:
- Ves-Losada, A. & Brenner, R.R. Mol Cell Biochem (1995) 142: 163. doi:10.1007/BF00928937
Activity of one of the key enzymes involved in arachidonic acid (20:4 n−6) biosynthesis, the Δ5 desaturase, was found in rat liver cell nuclei. Up to now, it has been shown that the fatty acid desaturases are located exclusively in the endoplasmic reticulum. Similarly to what happens with microsomal enzyme the nuclear Δ5 desaturase enzyme was only fully active in the presence of a cytosolic factor. In this condition it reached a specific activity of 50 pmol 20:4 n−6 formed/min/mg of protein. This fact would imply that purified nuclei like purified microsomes lack a soluble cytosol factor necessary for the total desaturation reaction expression. Besides the nuclear Δ5 desaturase has an optimal pH of 7.6 and is inhibited by 1 or 10 mM KCN. Low long chain acyl-CoA synthetase activity that catalyzes the formation of 20:3 n−6-CoA, was also found in liver nuclei. This step would be essential in nuclear desaturation since when ATP and/or CoA (necessary for the acylation reaction) are omitted from the incubation mixture, the desaturation reaction does not take place.
Key WordsΔ5 desaturaseacyl-CoA synthetasenucleifatty acid composition