On the capacity of the beta-oxidation of palmitate and palmitoyl-esters in rat liver mitochondria.
The beta-oxidation of palmitate, palmitoyl-CoA and palmitoyl-L-carnitine proceeded at a high rate in isolated rat liver mitochondria. At high concentrations (100 nmol/mg protein) the oxidation of palmitate and palmitoyl-CoA was only partly carnitine dependent. All substrates were most rapidly oxidized in the presence of oxaloacetate and state 3 conditions. Succinate inhibited beta-oxidation especially in state 4 conditions. beta-Oxidation was faster in hypotonic than in isotonic medium both in state 3 and state 4 conditions. Hypertonicity inhibited beta-oxidation. The initial formation of palmitoyl-CoA from palmitate, CoA and ATP was faster than the oxidation of palmitate under identical conditions. The presence of bovine serum albumin inhibited the beta-oxidation, especially with palmitoyl-CoA or free palmitate as the substrates. Mitochondria contain a palmitoyl-CoA hydrolase which may influence the available intramitochondrial palmitoyl-CoA. The present results demonstrate no single rate limiting step in the beta-oxidation in vitro. Both the NADH/NAD ratio, competition for the respiratory chain, the level of ADP, binding of palmitoyl-CoA to extramitochondrial protein, and possibly intramitochondrial hydrolysis of palmitoyl-CoA all seem to influence the rate of beta-oxidation in vitro. It is suggested that in vivo the most important factor is the availability of acyl-CoA to the outer carnitine palmitoyl-transferase of the mitochondria.
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002331:Carnitine / Q000031:analogs & derivatives*; D003065:Coenzyme A / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000201:enzymology / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010168:Palmitates / Q000378:metabolism*; D010169:Palmitic Acids / Q000378:metabolism*; D010171:Palmitoyl Coenzyme A / Q000096:biosynthesis / Q000378:metabolism*; D010170:Palmitoyl-CoA Hydrolase / Q000378:metabolism; D010172:Palmitoylcarnitine / Q000378:metabolism*; D051381:Rats
D000214:Acyl Coenzyme A; D010168:Palmitates; D010169:Palmitic Acids; D009243:NAD; D002245:Carbon Dioxide; D010171:Palmitoyl Coenzyme A; D010172:Palmitoylcarnitine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010170:Palmitoyl-CoA Hydrolase; D002331:Carnitine; D003065:Coenzyme A