Carnitine palmitoyltransferase activities: effects of serum albumin, acyl-CoA binding protein and fatty acid binding protein.
The carnitine palmitoyltransferase activity of various subcellular preparations measured with octanoyl-CoA as substrate was markedly increased by bovine serum albumin at low microM concentrations of octanoyl-CoA. However, even a large excess (500 microM) of this acyl-CoA did not inhibit the activity of the mitochondrial outer carnitine palmitoyltransferase, a carnitine palmitoyltransferase isoform that is particularly sensitive to inhibition by low microM concentrations of palmitoyl-CoA. This bovine serum albumin stimulation was independent of the salt activation of the carnitine palmitoyltransferase activity. The effects of acyl-CoA binding protein (ACBP) and the fatty acid binding protein were also examined with palmitoyl-CoA as substrate. The results were in line with the findings of stronger binding of acyl-CoA to ACBP but showed that fatty acid binding protein also binds acyl-CoA esters. Although the effects of these proteins on the outer mitochondrial carnitine palmitoyltransferase activity and its malonyl-CoA inhibition varied with the experimental conditions, they showed that the various carnitine palmitoyltransferase preparations are effectively able to use palmitoyl-CoA bound to ACBP in a near physiological molar ratio of 1:1 as well as that bound to the fatty acid binding protein. It is suggested that the three proteins mentioned above affect the carnitine palmitoyltransferase activities not only by binding of acyl-CoAs, preventing acyl-CoA inhibition, but also by facilitating the removal of the acylcarnitine product from carnitine palmitoyltransferase. These results support the possibility that the acyl-CoA binding ability of acyl-CoA binding protein and of fatty acid binding protein have a role in acyl-CoA metabolism in vivo.
Bhuiyan
A K
AK
Laboratory of Intermediary Metabolism, Clinical Research Institute of Montreal, Quebec, Canada.
Pande
S V
SV
D000214:Acyl Coenzyme A / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism*; D002352:Carrier Proteins / Q000494:pharmacology*; D026261:Diazepam Binding Inhibitor; D004789:Enzyme Activation; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology; D007527:Isoenzymes / Q000378:metabolism; D008316:Malonyl Coenzyme A / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000201:enzymology*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010171:Palmitoyl Coenzyme A / Q000378:metabolism; D051381:Rats; D012710:Serum Albumin, Bovine / Q000494:pharmacology*
D000214:Acyl Coenzyme A; D002352:Carrier Proteins; D026261:Diazepam Binding Inhibitor; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D007527:Isoenzymes; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; C034681:octanoyl-coenzyme A; D010171:Palmitoyl Coenzyme A; D012710:Serum Albumin, Bovine; D008316:Malonyl Coenzyme A; D002334:Carnitine O-Palmitoyltransferase