Carnitine acyltransferase activities in rat liver and heart measured with palmitoyl-CoA and octanoyl-CoA. Latency, effects of K+, bivalent metal ions and malonyl-CoA.
1. Liver carnitine acyltransferase activities with palmitoyl-CoA and octanoyl-CoA as substrates and heart carnitine palmitoyltransferase were measured as overt activities in whole mitochondria or in mitochondria disrupted by sonication or detergent treatment. All measurements were made in sucrose/KCl-based media of 300 mosmol/litre. 2. In liver mitochondria, acyltransferase measured with octanoyl-CoA, like carnitine palmitoyltransferase, was found to have latent and overt activities. 3. Liver acyltransferase activities measured with octanoyl-CoA and palmitoyl-CoA differed in their response to changes in [K+], Triton X-100 treatment and, in particular, in their response to Mg2+. Mg2+ stimulated activity with octanoyl-CoA, but inhibited carnitine palmitoyltransferase. 4. The effects of K+ and Mg2+ on liver overt carnitine palmitoyltransferase activity were abolished by Triton X-100 treatment. 5. Heart overt carnitine palmitoyltransferase activity differed from the corresponding activity in liver in that it was more sensitive to changes in [K+] and was stimulated by Mg2+. Heart had less latent carnitine palmitoyltransferase activity than did liver. 6. Overt carnitine palmitoyltransferase in heart mitochondria was extremely sensitive to inhibition by malonyl-CoA. Triton X-100 abolished the effect of low concentrations of malonyl-CoA on this activity. 7. The inhibitory effect of malonyl-CoA on heart carnitine palmitoyltransferase could be overcome by increasing the concentration of palmitoyl-CoA.
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D002333:Carnitine Acyltransferases / Q000378:metabolism*; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008316:Malonyl Coenzyme A / Q000494:pharmacology; D008929:Mitochondria, Heart / Q000187:drug effects / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology*; D010171:Palmitoyl Coenzyme A / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D000214:Acyl Coenzyme A; C034681:octanoyl-coenzyme A; D010171:Palmitoyl Coenzyme A; D008316:Malonyl Coenzyme A; D000217:Acyltransferases; D002333:Carnitine Acyltransferases; D002334:Carnitine O-Palmitoyltransferase; D002950:Citrate (si)-Synthase; D008274:Magnesium; D011188:Potassium