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Enzymes of carnitine acylation. Is overt carnitine palmitoyltransferase of liver peroxisomal carnitine octanoyltransferase?

ABSTRACT: Liver mitochondria prepared by differential centrifugation are contaminated by significant quantities of peroxisomes and microsomal fractions. 'Easily solubilized carnitine palmitoyltransferase' prepared from liver mitochondria is thought to originate from the outer surface of the mitochondrial inner membrane. We have characterized the carnitine palmitoyltransferase activities of freeze-thaw extracts of rat liver mitochondrial preparations. Chromatography on Sephadex G-100 yields two broad peaks of carnitine decanoyltransferase activity: one eluted at the end of the void volume, which can be removed (precipitated) by ultracentrifugation; the second peak represents the soluble activity and is eluted at an Mr near 70,000. The activity in the soluble peak is precipitated by an antibody raised against carnitine octanoyltransferase purified from mouse liver peroxisomes. In contrast, antibody raised against carnitine palmitoyltransferase purified from liver mitochondrial membranes had no effect (P. Brady & L. Brady, personal communication). The carnitine acyltransferase activities of the Mr-70,000 peak in the presence or absence of Tween 20 showed maximum activity with decanoyl-CoA and about one-third of this activity with palmitoyl-CoA, similar to peroxisomal carnitine octanoyltransferase. These data show that 7500 g preparations of liver mitochondria isolated by differential centrifugation are enriched by peroxisomal carnitine octanoyltransferase (approx. 20% of the protein of the fraction is peroxisomal) and indicate that this enzyme may be the one reported as 'overt' or 'easily solubilized' mitochondrial carnitine palmitoyltransferase.

SUBMITTER: Healy MJ

PROVIDER: S-EPMC1148689 | biostudies-other | 1988 Jan

REPOSITORIES: biostudies-other

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The relationship of rat liver overt carnitine palmitoyltransferase to the mitochondrial malonyl-CoA binding entity and to the latent palmitoyltransferase.

Project description:1. Confirming previous work [Murthy & Pande (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 378-382], malonyl-CoA-inhibitable carnitine palmitoyltransferase (CPT1) from rat liver was found to be localized in outer rather than in inner mitochondrial membranes. 2. Antisera were raised against a liver mitochondrial CPT of Mr 68,000, which was presumed to be the latent from of the enzyme (CPT2). These antisera cross-reacted with solubilized CPT extracted from liver inner mitochondrial membranes and with polypeptides of Mr 68,000 and 60,000 in immunoblots of both inner and outer mitochondrial membranes. The antisera also precipitated CPT activity from detergent-treated total membrane and outer-membrane preparations. 3. The antisera did not precipitate [14C]malonyl-CoA binding material obtained either from total membranes or from outer membranes. 4. It was concluded that liver CPT1 and CPT2 have some epitopes in common and may have a similar subunit size. In addition, CPT1 and the entity that binds malonyl-CoA must be separated polypeptides.

| S-EPMC1131802 | biostudies-other

Acute liver carnitine palmitoyltransferase I overexpression recapitulates reduced palmitate oxidation of cardiac hypertrophy.

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Missed Newborn Screening Case of Carnitine Palmitoyltransferase-II Deficiency.

Project description:Carnitine palmitoyltransferase-II (CPT-II) deficiency can be detected through newborn screening with tandem mass spectrometry. We report a 4-year-old patient with rhabdomyolysis due to CPT-II deficiency, which was initially missed by newborn screening. The patient presented with a 2-day history of fevers, upper respiratory infection, diffuse myalgia, and tea-colored urine. Her medical history was notable for frequent diffuse myalgia when ill. She was demonstrated to have homozygous mutation c.338C>T, p. S113L in CPT2, which is typically found in the adult-onset, myopathic form of the disease. An unknown number of CPT-II deficient patients with normal newborn screening have not yet presented to medical care with the adult-onset, myopathic form of disease. We conclude that (1) not all cases of CPT-II deficiency are currently detected through newborn screening, even when blood is appropriately collected on day 2 of life and (2) CPT-II deficiency should be kept on the differential for patients presenting with rhabdomyolysis, even if the newborn screening results were normal.

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Carnitine Palmitoyltransferase 1 Regulates Prostate Cancer Growth under Hypoxia.

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| S-EPMC8699124 | biostudies-literature

Loss of carnitine palmitoyltransferase 1a reduces docosahexaenoic acid-containing phospholipids and drives sexually dimorphic liver disease in mice.

Project description:Background and aimsGenome and epigenome wide association studies identified variants in carnitine palmitoyltransferase 1a (CPT1a) that associate with lipid traits. The goal of this study was to determine the role of liver-specific CPT1a on hepatic lipid metabolism.Approach and resultsMale and female liver-specific knockout (LKO) and littermate controls were placed on a low-fat or high-fat diet (60% kcal fat) for 15 weeks. Mice were necropsied after a 16 h fast, and tissues were collected for lipidomics, matrix-assisted laser desorption ionization mass spectrometry imaging, kinome analysis, RNA-sequencing, and protein expression by immunoblotting. Female LKO mice had increased serum alanine aminotransferase levels which were associated with greater deposition of hepatic lipids, while male mice were not affected by CPT1a deletion relative to male control mice. Mice with CPT1a deletion had reductions in DHA-containing phospholipids at the expense of monounsaturated fatty acids (MUFA)-containing phospholipids in whole liver and at the level of the lipid droplet (LD). Male and female LKO mice increased RNA levels of genes involved in LD lipolysis (Plin2, Cidec, G0S2) and in polyunsaturated fatty acid metabolism (Elovl5, Fads1, Elovl2), while only female LKO mice increased genes involved in inflammation (Ly6d, Mmp12, Cxcl2). Kinase profiling showed decreased protein kinase A activity, which coincided with increased PLIN2, PLIN5, and G0S2 protein levels and decreased triglyceride hydrolysis in LKO mice.ConclusionsLiver-specific deletion of CPT1a promotes sexually dimorphic steatotic liver disease (SLD) in mice, and here we have identified new mechanisms by which females are protected from HFD-induced liver injury.

| S-EPMC10568566 | biostudies-literature

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