ABSTRACT
In a screen for sterol regulatory element-binding protein (SREBP)-1c target genes in the liver, we identified long chain fatty acyl-CoA synthetase 5 (ACS-5). Hepatic ACS-5 mRNA is poorly expressed during fasting and diabetes and strongly induced by carbohydrate refeeding and insulin treatment. In cultured hepatocytes, insulin and a high glucose concentration induce ACS-5 mRNA. Adenoviral overexpression of a nuclear form of SREBP-1c in liver of diabetic mice or in cultured hepatocytes mimics the effect of insulin to induce ACS-5. By contrast, a dominant negative form of SREBP-1c abolishes the effect of insulin on ACS-5 expression. The dietary and SREBP-1c-mediated insulin regulation of ACS-5 expression indicate that ACS-5 is involved in the anabolic fate of fatty acids.
Subject(s)
Coenzyme A Ligases/biosynthesis , Coenzyme A Ligases/genetics , Coenzyme A Ligases/metabolism , Diabetes Mellitus, Experimental/physiopathology , Glucose/pharmacology , Insulin/pharmacology , Sterol Regulatory Element Binding Protein 1/physiology , Animals , Coenzyme A Ligases/drug effects , Eating , Enzyme Induction , Fasting , Fatty Acids/metabolism , Female , Liver/enzymology , Mitochondrial Proteins , Models, Animal , Polymerase Chain Reaction , RNA, Messenger/genetics , Rats , Rats, WistarABSTRACT
Many species of gram-positive bacteria produce branched peptidoglycan precursors resulting from the transfer of various L-amino acids or glycine from amino acyl-tRNA to the epsilon-amino group of L-lysine. The UDP-MurNAc-pentapeptide:L-alanine ligase and alanyl-tRNA synthetase genes from Enterococcus faecalis were identified, cloned, and overexpressed in Escherichia coli. The purified enzymes were necessary and sufficient for tRNA-dependent addition of L-alanine to UDP-MurNAc-pentapeptide in vitro. The ligase belonged to the Fem family of proteins, which were initially identified genetically as factors essential for methicillin resistance in Staphylococcus aureus.