Enzymatically inactive forms of acetyl-CoA carboxylase in rat liver mitochondria.
Biotinyl proteins were labelled by incubation of SDS-denatured preparations of subcellular fractions of rat liver with [14C]methylavidin before polyacrylamide-gel electrophoresis. Fluorographic analysis showed that mitochondria contained two forms of acetyl-CoA carboxylase [acetyl-CoA:carbon dioxide ligase (ADP-forming) EC 6.4.1.2], both of which were precipitated by antibody to the enzyme. When both forms were considered, almost three-quarters of the total liver acetyl-CoA carboxylase was found in the mitochondrial fraction of liver from fed rats while only 3.5% was associated with the microsomal fraction. The remainder was present in cytosol, either as the intact active enzyme or as a degradation product. The actual specific activity of the cytosolic enzyme was approx. 2 units/mg of acetyl-CoA carboxylase protein while that of the mitochondrial enzyme was about 20-fold lower, indicating that mitochondrial acetyl-CoA carboxylase was relatively inactive. Fractionation of mitochondria with digitonin showed that acetyl-CoA carboxylase was associated with the outer mitochondrial membrane. The available evidence suggests that mitochondrial acetyl-CoA carboxylase represents a reservoir of enzyme which can be released and activated under lipogenic conditions.
D000103:Acetyl-CoA Carboxylase / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D001710:Biotin / Q000032:analysis; D011232:Chemical Precipitation; D004072:Digitonin / Q000494:pharmacology; D007527:Isoenzymes / Q000276:immunology / Q000378:metabolism*; D008025:Ligases / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000201:enzymology
D007527:Isoenzymes; D001710:Biotin; D008025:Ligases; D000103:Acetyl-CoA Carboxylase; D004072:Digitonin