Rat heart expresses two forms of mitochondrial carnitine palmitoyltransferase I

The minor component is identical to the liver enzyme

Brian C. Weis, Victoria Esser, Daniel W. Foster, J. Denis McGarry

Research output: Contribution to journalArticle

108 Citations (Scopus)

Abstract

To begin to explore the basis for the tissue-specific expression of mitochondrial carnitine palmitoyltransferase I (CPT I), we focused on three rat tissues (liver, heart, and skeletal muscle) in which the enzyme was known to display very different properties. In Northern blot analysis, a cDNA probe corresponding to liver CPT I readily hybridized to a 4.5-kilobase species of mRNA in liver and heart, but not in skeletal muscle. Using the same probe to screen a neonatal rat heart cDNA library, a full-length clone, surprisingly having 100% sequence identity to the liver CPT I cDNA, was isolated. The paradox was resolved by two additional experiments. First, in Western blots of mitochondrial membranes, an antibody raised against liver CPT I recognized the 88-kDa protein in heart, as well as in liver, but not in skeletal muscle. Second, high specific activity [3H]deschloroetomoxir (a covalent ligand for CPT I) reacted with a single form of CPTI in liver (∼88 kDa) and skeletal muscle (∼82 kDa), while proteins of both sizes were labeled in the cardiac myocyte. Tritiated ligand binding to the two heart proteins was blocked by excess unlabeled malonyl-CoA. It is concluded that liver and skeletal muscle each contains a single and distinct isoform of CPT I with monomeric size of ∼88 and 82 kDa, respectively. The heart contains a CPT I protein of ∼82 kDa in size (probably identical to the skeletal muscle protein) but, importantly, also expresses the liver-type enzyme. The results likely explain why previous studies of heart CPT I yielded an apparent Km for carnitine and I50 value for malonyl-CoA inhibition that were intermediate between those of the liver and skeletal muscle enzymes.

Original languageEnglish (US)
Pages (from-to)18712-18715
Number of pages4
JournalJournal of Biological Chemistry
Volume269
Issue number29
StatePublished - Jul 22 1994

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Carnitine O-Palmitoyltransferase
Liver
Rats
Skeletal Muscle
Enzymes
Muscle
Malonyl Coenzyme A
Proteins
Complementary DNA
Tissue
Ligands
Carnitine
Muscle Proteins
Mitochondrial Membranes
Gene Library
Cardiac Myocytes
Northern Blotting
Myocardium
Protein Isoforms
Clone Cells

ASJC Scopus subject areas

  • Biochemistry

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Rat heart expresses two forms of mitochondrial carnitine palmitoyltransferase I : The minor component is identical to the liver enzyme. / Weis, Brian C.; Esser, Victoria; Foster, Daniel W.; McGarry, J. Denis.

In: Journal of Biological Chemistry, Vol. 269, No. 29, 22.07.1994, p. 18712-18715.

Research output: Contribution to journalArticle

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