Pig liver carnitine palmitoyltransferase I, with low Km for carnitine and high sensitivity to malonyl-CoA inhibition, is a natural chimera of rat liver and muscle enzymes.
The outer mitochondrial membrane enzyme carnitine palmitoyltransferase I (CPTI) catalyzes the initial and regulatory step in the beta-oxidation of fatty acids. The genes for the two isoforms of CPTI-liver (L-CPTI) and muscle (M-CPTI) have been cloned and expressed, and the genes encode for enzymes with very different kinetic properties and sensitivity to malonyl-CoA inhibition. Pig L-CPTI encodes for a 772 amino acid protein that shares 86 and 62% identity, respectively, with rat L- and M-CPTI. When expressed in Pichia pastoris, the pig L-CPTI enzyme shows kinetic characteristics (carnitine, K(m) = 126 microM; palmitoyl-CoA, K(m) = 35 microM) similar to human or rat L-CPTI. However, the pig enzyme, unlike the rat liver enzyme, shows a much higher sensitivity to malonyl-CoA inhibition (IC(50) = 141 nM) that is characteristic of human or rat M-CPTI enzymes. Therefore, pig L-CPTI behaves like a natural chimera of the L- and M-CPTI isotypes, which makes it a useful model to study the structure--function relationships of the CPTI enzymes.
Nicot
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Department of Biochemistry and Molecular Biology, University of Barcelona, School of Pharmacy, 08028 Barcelona, Spain.
Hegardt
F G
FG
Woldegiorgis
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G
Haro
D
D
Marrero
P F
PF
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism*; D002334:Carnitine O-Palmitoyltransferase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000302:isolation & purification; D004791:Enzyme Inhibitors / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008316:Malonyl Coenzyme A / Q000378:metabolism*; D051379:Mice; D008930:Mitochondria, Liver / Q000201:enzymology*; D008931:Mitochondria, Muscle / Q000201:enzymology*; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics; D010843:Pichia / Q000235:genetics; D051381:Rats; D016415:Sequence Alignment; D013552:Swine
D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D007527:Isoenzymes; C116917:acylcarnitine; D008316:Malonyl Coenzyme A; D002334:Carnitine O-Palmitoyltransferase; D002331:Carnitine