Carnitine metabolism (Homo sapiens)

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14235, 12, 174, 18, 21, 247, 8, 10, 15, 16, 19...2131, 3, 5, 6, 9...1, 3, 5, 6, 9...22mitochondrial matrixmitochondrial intermembrane spacecytosolnucleoplasmATPCoA-SHHCO3-ATPPALM-CoAAMPK heterotrimer(active)CoA-SHSLC22A5L-PCARNPRKAB2 MID1IP1RXRA ADPCARMal-CoACARAc-CoACARMID1IP1 Na+THRSP CITCPT1A,BPiNa+PPARD ADPPalmCoAp-T172-PRKAA2 CPT2RXRA:PPARD:atRATHRSPL-PCARNBtn-ACACB:2Mn2+polymerMID1IP1:THRSPCPT1A Btn-p-S79-ACACB:2Mn2+ polymeratRA SLC25A20PRKAG2 CPT1B Btn-ACACA:2Mn2+polymerCAR


Description

The mitochondrial carnitine system catalyzes the transport of long-chain fatty acids into the mitochondrial matrix where they undergo beta oxidation. This transport system consists of the malonyl-CoA sensitive carnitine palmitoyltransferase I (CPT-I) localized in the mitochondrial outer membrane, the carnitine:acylcarnitine translocase, an integral inner membrane protein, and carnitine palmitoyltransferase II localized on the matrix side of the inner membrane. (Kerner and Hoppel, 2000). View original pathway at Reactome.

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Reactome-Converter 
Pathway is converted from Reactome ID: 200425
Reactome-version 
Reactome version: 73
Reactome Author 
Reactome Author: Gopinathrao, G

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Bibliography

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  1. IJlst L, Mandel H, Oostheim W, Ruiter JP, Gutman A, Wanders RJ.; ''Molecular basis of hepatic carnitine palmitoyltransferase I deficiency.''; PubMed Europe PMC Scholia
  2. Verderio E, Cavadini P, Montermini L, Wang H, Lamantea E, Finocchiaro G, DiDonato S, Gellera C, Taroni F.; ''Carnitine palmitoyltransferase II deficiency: structure of the gene and characterization of two novel disease-causing mutations.''; PubMed Europe PMC Scholia
  3. Aipoalani DL, O'Callaghan BL, Mashek DG, Mariash CN, Towle HC.; ''Overlapping roles of the glucose-responsive genes, S14 and S14R, in hepatic lipogenesis.''; PubMed Europe PMC Scholia
  4. Zhu H, Shi J, de Vries Y, Arvidson DN, Cregg JM, Woldegiorgis G.; ''Functional studies of yeast-expressed human heart muscle carnitine palmitoyltransferase I.''; PubMed Europe PMC Scholia
  5. Ramsay RR, Gandour RD, van der Leij FR.; ''Molecular enzymology of carnitine transfer and transport.''; PubMed Europe PMC Scholia
  6. Abu-Elheiga L, Brinkley WR, Zhong L, Chirala SS, Woldegiorgis G, Wakil SJ.; ''The subcellular localization of acetyl-CoA carboxylase 2.''; PubMed Europe PMC Scholia
  7. Morillas M, Gómez-Puertas P, Rubí B, Clotet J, Ariño J, Valencia A, Hegardt FG, Serra D, Asins G.; ''Structural model of a malonyl-CoA-binding site of carnitine octanoyltransferase and carnitine palmitoyltransferase I: mutational analysis of a malonyl-CoA affinity domain.''; PubMed Europe PMC Scholia
  8. Kim CW, Moon YA, Park SW, Cheng D, Kwon HJ, Horton JD.; ''Induced polymerization of mammalian acetyl-CoA carboxylase by MIG12 provides a tertiary level of regulation of fatty acid synthesis.''; PubMed Europe PMC Scholia
  9. Ruderman N, Prentki M.; ''AMP kinase and malonyl-CoA: targets for therapy of the metabolic syndrome.''; PubMed Europe PMC Scholia
  10. Tsatsos NG, Augustin LB, Anderson GW, Towle HC, Mariash CN.; ''Hepatic expression of the SPOT 14 (S14) paralog S14-related (Mid1 interacting protein) is regulated by dietary carbohydrate.''; PubMed Europe PMC Scholia
  11. Zammit VA, Price NT, Fraser F, Jackson VN.; ''Structure-function relationships of the liver and muscle isoforms of carnitine palmitoyltransferase I.''; PubMed Europe PMC Scholia
  12. Longo N, Frigeni M, Pasquali M.; ''Carnitine transport and fatty acid oxidation.''; PubMed Europe PMC Scholia
  13. Huizing M, Iacobazzi V, Ijlst L, Savelkoul P, Ruitenbeek W, van den Heuvel L, Indiveri C, Smeitink J, Trijbels F, Wanders R, Palmieri F.; ''Cloning of the human carnitine-acylcarnitine carrier cDNA and identification of the molecular defect in a patient.''; PubMed Europe PMC Scholia
  14. Ingaramo M, Beckett D.; ''Selectivity in post-translational biotin addition to five human carboxylases.''; PubMed Europe PMC Scholia
  15. Bay DC, Court DA.; ''Origami in the outer membrane: the transmembrane arrangement of mitochondrial porins.''; PubMed Europe PMC Scholia
  16. Tamai I, Ohashi R, Nezu J, Yabuuchi H, Oku A, Shimane M, Sai Y, Tsuji A.; ''Molecular and functional identification of sodium ion-dependent, high affinity human carnitine transporter OCTN2.''; PubMed Europe PMC Scholia
  17. Kerner J, Hoppel C.; ''Genetic disorders of carnitine metabolism and their nutritional management.''; PubMed Europe PMC Scholia
  18. Seth P, Wu X, Huang W, Leibach FH, Ganapathy V.; ''Mutations in novel organic cation transporter (OCTN2), an organic cation/carnitine transporter, with differential effects on the organic cation transport function and the carnitine transport function.''; PubMed Europe PMC Scholia
  19. Gobin S, Thuillier L, Jogl G, Faye A, Tong L, Chi M, Bonnefont JP, Girard J, Prip-Buus C.; ''Functional and structural basis of carnitine palmitoyltransferase 1A deficiency.''; PubMed Europe PMC Scholia
  20. Park S, Hwang IW, Makishima Y, Perales-Clemente E, Kato T, Niederländer NJ, Park EY, Terzic A.; ''Spot14/Mig12 heterocomplex sequesters polymerization and restrains catalytic function of human acetyl-CoA carboxylase 2.''; PubMed Europe PMC Scholia
  21. Morillas M, López-Viñas E, Valencia A, Serra D, Gómez-Puertas P, Hegardt FG, Asins G.; ''Structural model of carnitine palmitoyltransferase I based on the carnitine acetyltransferase crystal.''; PubMed Europe PMC Scholia
  22. Kim KW, Yamane H, Zondlo J, Busby J, Wang M.; ''Expression, purification, and characterization of human acetyl-CoA carboxylase 2.''; PubMed Europe PMC Scholia
  23. Abu-Elheiga L, Almarza-Ortega DB, Baldini A, Wakil SJ.; ''Human acetyl-CoA carboxylase 2. Molecular cloning, characterization, chromosomal mapping, and evidence for two isoforms.''; PubMed Europe PMC Scholia
  24. Amengual J, Petrov P, Bonet ML, Ribot J, Palou A.; ''Induction of carnitine palmitoyl transferase 1 and fatty acid oxidation by retinoic acid in HepG2 cells.''; PubMed Europe PMC Scholia

History

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CompareRevisionActionTimeUserComment
113370view11:44, 2 November 2020ReactomeTeamReactome version 74
112574view15:54, 9 October 2020ReactomeTeamReactome version 73
101488view11:34, 1 November 2018ReactomeTeamreactome version 66
101025view21:14, 31 October 2018ReactomeTeamreactome version 65
100560view19:48, 31 October 2018ReactomeTeamreactome version 64
100108view16:33, 31 October 2018ReactomeTeamreactome version 63
99658view15:04, 31 October 2018ReactomeTeamreactome version 62 (2nd attempt)
99259view12:45, 31 October 2018ReactomeTeamreactome version 62
93356view11:21, 9 August 2017ReactomeTeamNew pathway

External references

DataNodes

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NameTypeDatabase referenceComment
ADPMetaboliteCHEBI:456216 (ChEBI)
AMPK heterotrimer (active)ComplexR-HSA-200408 (Reactome)
ATPMetaboliteCHEBI:30616 (ChEBI)
Ac-CoAMetaboliteCHEBI:15351 (ChEBI)
Btn-ACACA:2Mn2+ polymerR-HSA-8876883 (Reactome)
Btn-ACACB:2Mn2+ polymerR-HSA-8867341 (Reactome)
Btn-p-S79-ACACB:2Mn2+ polymerR-HSA-8876893 (Reactome)
CARMetaboliteCHEBI:17126 (ChEBI)
CITMetaboliteCHEBI:30769 (ChEBI)
CPT1A ProteinP50416 (Uniprot-TrEMBL)
CPT1A,BComplexR-HSA-549205 (Reactome)
CPT1B ProteinQ92523 (Uniprot-TrEMBL)
CPT2ProteinP23786 (Uniprot-TrEMBL)
CoA-SHMetaboliteCHEBI:15346 (ChEBI)
HCO3-MetaboliteCHEBI:17544 (ChEBI)
L-PCARNMetaboliteCHEBI:17490 (ChEBI)
MID1IP1 ProteinQ9NPA3 (Uniprot-TrEMBL)
MID1IP1:THRSPComplexR-HSA-8867329 (Reactome)
MID1IP1ProteinQ9NPA3 (Uniprot-TrEMBL)
Mal-CoAMetaboliteCHEBI:15531 (ChEBI)
Na+MetaboliteCHEBI:29101 (ChEBI)
PALM-CoAMetaboliteCHEBI:15525 (ChEBI)
PPARD ProteinQ03181 (Uniprot-TrEMBL)
PRKAB2 ProteinO43741 (Uniprot-TrEMBL)
PRKAG2 ProteinQ9UGJ0 (Uniprot-TrEMBL)
PalmCoAMetaboliteCHEBI:15525 (ChEBI)
PiMetaboliteCHEBI:18367 (ChEBI)
RXRA ProteinP19793 (Uniprot-TrEMBL)
RXRA:PPARD:atRAComplexR-HSA-5634107 (Reactome)
SLC22A5ProteinO76082 (Uniprot-TrEMBL)
SLC25A20ProteinO43772 (Uniprot-TrEMBL)
THRSP ProteinQ92748 (Uniprot-TrEMBL)
THRSPProteinQ92748 (Uniprot-TrEMBL)
atRA MetaboliteCHEBI:15367 (ChEBI)
p-T172-PRKAA2 ProteinP54646 (Uniprot-TrEMBL)

Annotated Interactions

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SourceTargetTypeDatabase referenceComment
ADPArrowR-HSA-200423 (Reactome)
ADPArrowR-HSA-75851 (Reactome)
ADPArrowR-HSA-8876889 (Reactome)
AMPK heterotrimer (active)mim-catalysisR-HSA-200423 (Reactome)
ATPR-HSA-200423 (Reactome)
ATPR-HSA-75851 (Reactome)
ATPR-HSA-8876889 (Reactome)
Ac-CoAR-HSA-75851 (Reactome)
Ac-CoAR-HSA-8876889 (Reactome)
Btn-ACACA:2Mn2+ polymermim-catalysisR-HSA-75851 (Reactome)
Btn-ACACB:2Mn2+ polymerR-HSA-200423 (Reactome)
Btn-ACACB:2Mn2+ polymermim-catalysisR-HSA-8876889 (Reactome)
Btn-p-S79-ACACB:2Mn2+ polymerArrowR-HSA-200423 (Reactome)
CARArrowR-HSA-165026 (Reactome)
CARArrowR-HSA-200410 (Reactome)
CARArrowR-HSA-200424 (Reactome)
CARArrowR-HSA-8949399 (Reactome)
CARR-HSA-165026 (Reactome)
CARR-HSA-200406 (Reactome)
CARR-HSA-200424 (Reactome)
CARR-HSA-8949399 (Reactome)
CITArrowR-HSA-75851 (Reactome)
CITArrowR-HSA-8876889 (Reactome)
CPT1A,Bmim-catalysisR-HSA-200406 (Reactome)
CPT2mim-catalysisR-HSA-200410 (Reactome)
CoA-SHArrowR-HSA-200406 (Reactome)
CoA-SHR-HSA-200410 (Reactome)
HCO3-R-HSA-75851 (Reactome)
HCO3-R-HSA-8876889 (Reactome)
L-PCARNArrowR-HSA-200406 (Reactome)
L-PCARNArrowR-HSA-200424 (Reactome)
L-PCARNR-HSA-200410 (Reactome)
L-PCARNR-HSA-200424 (Reactome)
MID1IP1:THRSPArrowR-HSA-75851 (Reactome)
MID1IP1:THRSPArrowR-HSA-8866941 (Reactome)
MID1IP1:THRSPArrowR-HSA-8876889 (Reactome)
MID1IP1R-HSA-8866941 (Reactome)
Mal-CoAArrowR-HSA-75851 (Reactome)
Mal-CoAArrowR-HSA-8876889 (Reactome)
Mal-CoATBarR-HSA-200406 (Reactome)
Na+ArrowR-HSA-165026 (Reactome)
Na+R-HSA-165026 (Reactome)
PALM-CoAR-HSA-200406 (Reactome)
PalmCoAArrowR-HSA-200410 (Reactome)
PiArrowR-HSA-75851 (Reactome)
PiArrowR-HSA-8876889 (Reactome)
R-HSA-165026 (Reactome) OCTN2 (organic cation transporter novel 2, encoded by the SLC22A5 gene) mediates the sodium-dependent transport of CAR (carnitine) from the extracellular space into the cytosol.

While humans are capable of synthesizing carnitine de novo, the enzyme that catalyzes the last reaction of the biosynthetic pathway is found only in liver and kidney cells, and at very low levels in brain cells. Other tissues that require carnitine, such as muscle, are dependent on transport systems that mediate its export from the liver and uptake by other tissues (Kerner & Hoppel 1998). The specific transport systems responsible for liver export have been characterized biochemically in model organisms but specific transport proteins have not yet been identified. OCTN2 is the major transporter responsible for carnitine uptake in extrahepatic tissues, as demonstrated both by the biochemical characterization of overexpressed recombinant human protein (Tamai et al. 1998) and by the appearance of symptoms of carnitine deficiency in humans lacking a functional SLC22A5 gene (Seth et al. 1999; reviewed by Longo et al. 2016).

R-HSA-200406 (Reactome) Carnitine palmitoyl transferase 1 (CPT1) associated with the inner mitochondrial membrane, catalyzes the reaction of palmitoyl-CoA (PALM-CoA) from the cytosol with carnitine (CAR) in the mitochondrial intermembrane space to form palmitoylcarnitine (L-PCARN) and CoA-SH. Three CPT1 isoforms exist; CPT1A, B and C. In the body, CPT1A is most abundant in liver while CPT1B is abundant in muscle. CPT1C is mainly expressed in neurons and localises to the ER and not to the mitochondria. It has little or no enzymatic activity in fatty acid oxidation. Both CPT1A and CPT1B are inhibited by malonyl-CoA (Morillas et al. 2002, 2004; Zammit et al. 2001; Zhu et al. 1997). Mutations in CPT1A are associated with defects in fatty acid metabolism and fasting intolerance, consistent with the role assigned to CPT1 from studies in vitro and in animal models (IJlst et al. 1998; Gobin et al. 2003).
In the nucleus, cellular retinoic acid-binding protein 1 or 2 (CRABP1 or 2), bound to all-trans-retinoic acid (atRA), directly binds to the heterodimeric complex of retinoic acid receptor alpha RXRA) and peroxisome proliferator-activated receptor delta (PPARD). When bound to PPARD, atRA can significantly increase the expression of proteins involved in fatty acid oxidation such as CPT1A via its induction of PPARD (Amengual et al. 2012).
R-HSA-200410 (Reactome) CPT2, associated with the inner mitochondrial membrane, catalyzes the reaction of palmitoylcarnitine and CoASH to form palmitoyl-CoA and carnitine (Verderio et al. 1995).
R-HSA-200423 (Reactome) Acetyl-CoA carboxylase 2 (ACACB, ACC2) is involved in the regulation of mitochondrial fatty acid oxidation through the inhibition of carnitine palmitoyltransferase 1 by its product malonyl-CoA. Phosphorylated AMPK inactivates ACACB in muscle cells by phosphorylation. This results in decreased levels of malonyl CoA, contributing to the homeostasis of mitochondrial beta oxidation (Ruderman & Prentki 2004).
R-HSA-200424 (Reactome) The carnitine-acylcarnitine transporter (SLC25A20 / CACT), embedded in the inner mitochondrial membrane, mediates the exchange of palmitoyl-carnitine (and other acylcarnitine esters) and carnitine across the inner mitochondrial membrane (Huizing et al., 1997).
R-HSA-75851 (Reactome) Cytosolic acetyl-CoA carboxylase 1 (ACACA) catalyzes the reaction of bicarbonate, ATP, and acetyl-CoA to form malonyl-CoA, ADP, and orthophosphate. The reaction is positively regulated by citrate. The human ACACA cDNA has been cloned (Abu-Elheiga et al. 1995) and the biochemical properties of the human enzyme have recently been described (Cheng et al. 2007; Locke et al. 2008). Four ACACA isoforms generated by alternative splicing have been identified as mRNAs - the protein product of the first has been characterized experimentally. ACACA uses biotin (Btn) and two Mn2+ ions per subunit as cofactors and its activity is increased by polymerisation (Kim et al. 2010, Ingaramo & Beckett 2012). Cytosolic ACACA is thought to maintain regulation of fatty acid synthesis in all tissues but especially lipogenic tissues such as adipose tissue and lactating mammary glands.

Mid1-interacting protein 1 (MID1IP1, aka MIG12, SPOT14R, S14R) plays a role in the regulation of lipogenesis in the liver. It is rapidly upregulated by processes that induce lipogenesis (enhanced glucose metabolism, thyroid hormone administration) (Tsatsos et al. 2008). MID1IP1 forms a heterodimer with thyroid hormone-inducible hepatic protein (THRSP, aka SPOT14, S14), proposed to play the same role in lipogenesis as MID1IP1 (Aipoalani et al. 2010). This complex can polymerise acetyl-CoA carboxylases 1 and 2 (ACACA and B), the first committed enzymes in fatty acid (FA) synthesis. Polymerisation enhances ACACA and ACACB enzyme activities (Kim et al. 2010).
R-HSA-8866941 (Reactome) Mid1-interacting protein 1 (MID1IP1, aka MIG12, SPOT14R, S14R) plays a role in the regulation of lipogenesis in the liver. It is rapidly upregulated by processes that induce lipogenesis (enhanced glucose metabolism, thyroid hormone administration) (Tsatsos et al. 2008). MID1IP1 forms a heterodimer with thyroid hormone-inducible hepatic protein (THRSP, aka SPOT14, S14), proposed to play the same role in lipogenesis as MID1IP1 (Aipoalani et al. 2010). This complex can polymerise acetyl-CoA carboxylases 1 and 2 (ACACA and B), the first committed enzymes in fatty acid (FA) synthesis. Polymerisation enhances ACACA and ACACB enzyme activities (Kim et al. 2010, Park et al. 2013).
R-HSA-8876889 (Reactome) Mitochondrial acetyl-CoA carboxylase 2 (ACACB, ACC2) (Kim et al. 2007) catalyses the reaction of bicarbonate, ATP, and acetyl-CoA to form malonyl-CoA, ADP, and orthophosphate. The reaction is positively regulated by citrate. ACACB uses biotin (Btn) and two Mn2+ ions per subunit as cofactors and its activity is increased by polymerisation (Kim et al. 2010, Ingaramo & Beckett 2012). ACACB is located on the outer mitochondrial membrane and is involved in the regulation of mitochondrial fatty acid oxidation through the inhibition of carnitine palmitoyltransferase 1 by its product malonyl-CoA (Abu-Elheiga et al. 2000).

Mid1-interacting protein 1 (MID1IP1, aka MIG12, SPOT14R, S14R) plays a role in the regulation of lipogenesis in the liver. It is rapidly upregulated by processes that induce lipogenesis (enhanced glucose metabolism, thyroid hormone administration) (Tsatsos et al. 2008). MID1IP1 forms a heterodimer with thyroid hormone-inducible hepatic protein (THRSP, aka SPOT14, S14), proposed to play the same role in lipogenesis as MID1IP1 (Aipoalani et al. 2010). This complex can polymerise acetyl-CoA carboxylases 1 and 2 (ACACA and B), the first committed enzymes in fatty acid (FA) synthesis. Polymerisation enhances ACACA and ACACB enzyme activities (Kim et al. 2010).
R-HSA-8949399 (Reactome) CAR (carnitine) diffuses across the mitochondrial outer membrane from the cytosol to the mitochondrial intermembrane space, presumably via porin channels in the outer membrane (Bay & Court 2002).
RXRA:PPARD:atRAArrowR-HSA-200406 (Reactome)
SLC22A5mim-catalysisR-HSA-165026 (Reactome)
SLC25A20mim-catalysisR-HSA-200424 (Reactome)
THRSPR-HSA-8866941 (Reactome)
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