Fatty acid delta 5 desaturation in rat liver cell nuclei.
Activity of one of the key enzymes involved in arachidonic acid (20:4 n-6) biosynthesis, the delta 5 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 delta 5 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 delta 5 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.
Ves-Losada
A
A
Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Facultad de Ciencias Médicas, UNLP-CONICET, Argentina.
Brenner
R R
RR
D044942:Acyl-CoA Dehydrogenase, Long-Chain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000201:enzymology* / Q000648:ultrastructure; D003066:Coenzyme A Ligases / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology; D000090943:Delta-5 Fatty Acid Desaturase; D044943:Fatty Acid Desaturases; D005227:Fatty Acids / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D050356:Lipid Metabolism; D008099:Liver / Q000201:enzymology*; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D000098859:Long-Chain-Fatty-Acid-CoA Ligase
D000090943:Delta-5 Fatty Acid Desaturase; D005227:Fatty Acids; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D010664:Phenylmethylsulfonyl Fluoride; D044943:Fatty Acid Desaturases; D044942:Acyl-CoA Dehydrogenase, Long-Chain; D003066:Coenzyme A Ligases; C090799:FAA2 protein, S cerevisiae; D000098859:Long-Chain-Fatty-Acid-CoA Ligase; D011190:Potassium Cyanide