The activation of short-chain fatty acids by the soluble fraction of guinea-pig heart and liver mitochondria. The search for a distinct propionyl-CoA synthetase.
1. The ATP dependent acetyl-, propionyl- and butyryl-CoA synthetase activities were measured in the soluble fraction of both guinea-pig heart and liver mitochondria. 2. When measured in 300 mM Tris-HC1, the V of propionate activation in heart (equals 892 munits/mg protein) is much higher than the V of acetate (equals 637 munits/mg protein) and butyrate activation (equals 143 munits/mg protein. Fatty acid competition experiments, however, clearly show that most of the propionate activation (Km equals 7.94 mM) is caused by the acetyl-CoA synthetase (EC 6.2.1.1) (Km for acetate equals 0.8 mM), while the remaining activity is probably caused by a butyryl-CoA synthetase (Km for butyrate equals 0.83 mM). This indicates that in guinea-pig heart the presence of a distinct propionyl-CoA synthetase is very unlikely. 3. In liver a completely different pattern of short-chain fatty acid activation is found: low acetate activation and moderate propionate and butyrate activation. Substrate competition experiments and kinetics of fatty acid activation indicate that in this tissue a distinct propionyl-CoA synthetase is present with high affinity for propionate (Km equals 0.6 mM) and some affinity towards acetate and butyrate (Km values respectively 11 mM and 5.4 mM).
D000085:Acetates / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002087:Butyrates / Q000378:metabolism; D002250:Carbon Radioisotopes; D003066:Coenzyme A Ligases / Q000378:metabolism*; D006168:Guinea Pigs; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D011422:Propionates / Q000378:metabolism; D011485:Protein Binding
D000085:Acetates; D002087:Butyrates; D002250:Carbon Radioisotopes; D011422:Propionates; D003066:Coenzyme A Ligases