Pig liver carnitine palmitoyltransferase. Chimera studies show that both the N- and C-terminal regions of the enzyme are important for the unusual high malonyl-CoA sensitivity.
Pig and rat liver carnitine palmitoyltransferase I (L-CPTI) share common K(m) values for palmitoyl-CoA and carnitine. However, they differ widely in their sensitivity to malonyl-CoA inhibition. Thus, pig l-CPTI has an IC(50) for malonyl-CoA of 141 nm, while that of rat L-CPTI is 2 microm. Using chimeras between rat L-CPTI and pig L-CPTI, we show that the entire C-terminal region behaves as a single domain, which dictates the overall malonyl-CoA sensitivity of this enzyme. The degree of malonyl-CoA sensitivity is determined by the structure adopted by this domain. Using deletion mutation analysis, we show that malonyl-CoA sensitivity also depends on the interaction of this single domain with the first 18 N-terminal amino acid residues. We conclude that pig and rat L-CPTI have different malonyl-CoA sensitivity, because the first 18 N-terminal amino acid residues interact differently with the C-terminal domain. This is the first study that describes how interactions between the C- and N-terminal regions can determine the malonyl-CoA sensitivity of L-CPTI enzymes using active C-terminal chimeras.
Nicot
Carine
C
Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Barcelona, 08028 Barcelona, Spain.
Relat
Joana
J
Woldegiorgis
Gebre
G
Haro
Diego
D
Marrero
Pedro F
PF
D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015151:Immunoblotting; D020128:Inhibitory Concentration 50; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008316:Malonyl Coenzyme A / Q000378:metabolism*; D016296:Mutagenesis; D009154:Mutation; D010843:Pichia / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013552:Swine
D000596:Amino Acids; D011993:Recombinant Fusion Proteins; D008316:Malonyl Coenzyme A; D002334:Carnitine O-Palmitoyltransferase