Carnitine acetyltransferase. Effect of malonyl-CoA, fasting and clofibrate feeding in mitochondria from different tissues.
Malonyl-CoA sensitivity of carnitine acetyltransferase (EC 2.3.1.7) activities in isolated intact mitochondria from rat liver, heart and white and brown adipose tissue, and rabbit liver and heart were studied with a radioisotopic assay using [3H]acetyl-CoA. Malonyl-CoA inhibited [3H]acetylcarnitine formation in intact rat liver mitochondria (overt activity), while acetyltransferase in heart and white and brown adipose tissue were malonyl-CoA-insensitive. Acetyltransferase from rabbit liver and heart was only weakly inhibited by malonyl-CoA. Acetyltransferase in intact rat liver peroxisomes was malonyl-CoA-insensitive. Lysis of the mitochondria with (+)palmitoylcarnitine increased acetyltransferase activities (total activity) in all mitochondria studied and abolished malonyl-CoA-sensitivity, showing the necessity of intact mitochondrial membranes for malonyl-CoA-sensitivity. A differential increase in overt and total mitochondrial carnitine acetyltransferase was observed in rat liver upon fasting and clofibrate feeding. Fasting increased overt activity more than total activity and diminished malonyl-CoA-sensitivity. Clofibrate increased mainly total activity and also reduced malonyl-CoA-sensitivity. A similar pattern of increased activities was observed with palmitoyl-CoA and octanoyl-CoA as substrates.
D000123:Acetyltransferases / Q000378:metabolism*; D000214:Acyl Coenzyme A / Q000494:pharmacology*; D000273:Adipose Tissue / Q000201:enzymology; D002001:Adipose Tissue, Brown / Q000201:enzymology; D000818:Animals; D002332:Carnitine O-Acetyltransferase / Q000378:metabolism*; D002994:Clofibrate / Q000494:pharmacology*; D005215:Fasting; D007700:Kinetics; D008297:Male; D008316:Malonyl Coenzyme A / Q000494:pharmacology*; D008830:Microbodies / Q000201:enzymology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D008929:Mitochondria, Heart / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains
D000214:Acyl Coenzyme A; D008316:Malonyl Coenzyme A; D000123:Acetyltransferases; D002332:Carnitine O-Acetyltransferase; D002994:Clofibrate