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Coenzyme A overview

Coenzyme A Intermediates in Cellular Metabolism

Overview of Coenzyme A Intermediates

Coenzyme A (CoA) intermediates are essential molecules involved in cellular metabolism and energy production. CoA is synthesized via a highly conserved five-step biosynthetic pathway involving several critical metabolic intermediates [1-3]. These intermediates, such as 4'-phosphopantetheine and 3'-dephosphocoenzyme A, play vital roles not only as precursors in synthesis but also in cellular signaling, protein modification, and metabolic rescue [4-6]. 

3’-Dephosphocoenzyme A (dPCoA)

3'-Dephosphocoenzyme A (also known as dephospho-CoA) is the penultimate intermediate in the synthesis of CoA [2,5].

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  • Synthesis and conversion: It is formed from 4'-phosphopantetheine by the adenylyltransferase activity (PPAT) of the bifunctional enzyme COASY (CoA synthase). The final step of CoA biosynthesis involves the phosphorylation of the 3'-hydroxyl group of dPCoA’s ribose ring by dephospho-CoA kinase (DPCK), which is also a domain of the COASY enzyme [7,13].

  • Degradation and transport: dPCoA can be produced through the dephosphorylation of CoA by alkaline phosphatase (AP) in the intestine or lysosomal acid phosphatase (LAP) within cells [2,6]. Specific transporters, such as SLC25A42 in the inner mitochondrial membrane and SLC25A17 in the peroxisomal membrane, have been identified to facilitate the movement of dPCoA and CoA between subcellular compartments [14,15].

4'-Phosphopantetheine (PPanSH)

4’-Phosphopantetheine is one of the intermediates in the canonical CoA biosynthetic pathway [1,2]. It is produced intracellularly through the decarboxylation of 4’-phosphopantothenoylcysteine by the enzyme PPCDC [7].

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  • Extracellular stability and uptake: Unlike many other intermediates, 4’-phosphopantetheine is biologically stable in serum and does not undergo the rapid degradation seen with pantetheine, which is typically broken down by vanins (pantetheinases) into pantothenate and cysteamine [1,2,8]. This stability allows it to serve as a central metabolite that can be taken up by cells via passive diffusion [1,8].

  • Post-translational modification: It serves as the essential prosthetic group for mitochondrial acyl carrier protein (mtACP) [4,9]. In a process known as 4’-phosphopantetheinylation, the PPanSH moiety is transferred from CoA to a conserved serine residue on mtACP, converting it into its active holo-form [4,9,10].

  • Therapeutic Potential: Oral administration of 4’-phosphopantetheine has been shown to bypass early enzymatic blocks (such as those in PKAN, caused by PANK2 mutations) and restore intracellular CoA levels, effectively rescuing metabolic and neurodegenerative phenotypes in animal models [11,12].

4',4''-Diphosphopantethine

While less frequently discussed as a free intermediate, pantethine 4',4''-diphosphate is the oxidized (disulfide) form of 4'-phosphopantetheine. Research indicates that specific enzymes, such as those found in B. megaterium, act as disulfide reductases with high specificity for disulfides containing this phosphorylated moiety [16]. Chemically, CoA is often synthesized or targeted in its disulfide form to prevent the oxidation of the sulfur atom during production [3].

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The disulfide form (4',4''-diphosphopantethine) provides a more stable alternative for handling and processing and can be reduced under appropriate conditions to regenerate 4′-phosphopantetheine in reducing-compatible workflows. In contrast, the monomeric form is preferred in applications that are sensitive to reducing conditions or require immediate availability of the free thiol group.

References

  1. Srinivasan, B.; Baratashvili, M.; van der Zwaag, M.; Kanon, B.; Colombelli, C.; Lambrechts, R. A.; et al. Extracellular 4'-Phosphopantetheine Is a Source for Intracellular Coenzyme A Synthesis. Nat. Chem. Biol. 2015, 11 (10), 784–792. 

  2. Naquet, P.; Kerr, E. W.; Vickers, S. D.; Leonardi, R. Regulation of Coenzyme A Levels by Degradation: The ‘Ins and Outs’. Prog. Lipid Res. 2020, 78*, 101028. 

  3. Mouterde, L. M. M.; Stewart, J. D. Isolation and Synthesis of One of the Most Central Cofactors in Metabolism: Coenzyme A. Org. Process Res. Dev. 2019, 23 (1), 19–30. 

  4. Yu, Y.; Moretti, I. F.; Grzeschik, N. A.; Sibon, O. C. M.; Schepers, H. Coenzyme A Levels Influence Protein Acetylation, CoAlation and 4'-Phosphopantetheinylation: Expanding the Impact of a Metabolic Nexus Molecule. BBA - Mol. Cell Res. 2021, 1868 (4), 118965. 

  5. Mignani, L.; Gnutti, B.; Zizioli, D.; Finazzi, D. Coenzyme A Biochemistry: From Neurodevelopment to Neurodegeneration. Brain Sci. 2021, 11 (8), 1031. 

  6. Czumaj, A.; Szrok-Jurga, S.; Hebanowska, A.; Turyn, J.; Swierczynski, J.; Sledzinski, T.; Stelmanska, E. The Pathophysiological Role of CoA. Int. J. Mol. Sci. 2020, 21 (23), 9057. 

  7. Leonardi, R.; Jackowski, S. Coenzyme A Biosynthesis. EcoSal Plus 2007, 2 (2). 

  8. Sibon, O. C. M.; Strauss, E. Coenzyme A: To Make It or Uptake It? Nat. Rev. Mol. Cell Biol. 2016, 17 (10), 605–606. 

  9. Lambrechts, R. A.; Schepers, H.; Yu, Y.; van der Zwaag, M.; Autio, K. J.; Vieira-Lara, M. A.; et al. CoA-Dependent Activation of Mitochondrial Acyl Carrier Protein Links Four Neurodegenerative Diseases. EMBO Mol. Med. 2019, 11 (12), e10488. 

  10. Beld, J.; Sonnenschein, E. C.; Vickery, C. R.; Noel, J. P.; Burkart, M. D. The Phosphopantetheinyl Transferases: Catalysis of a Post-Translational Modification Crucial for Life. Nat. Prod. Rep. 2014, 31 (1), 61–108. 

  11. Jeong, S. Y.; Hogarth, P.; Placzek, A.; Gregory, A. M.; Fox, R.; Zhen, D.; et al. 4'-Phosphopantetheine Corrects CoA, Iron, and Dopamine Metabolic Defects in Mammalian Models of PKAN. EMBO Mol. Med. 2019, 11 (12), e10489. 

  12. Hayflick, S. J.; Jeong, S. Y.; Sibon, O. C. M. PKAN Pathogenesis and Treatment. Mol. Genet. Metab. 2022, 137 (3), 283–291. 

  13. Heckmann, K.; Iuso, A.; Reunert, J.; Koch, H. G.; Ohno, K.; Laugwitz, K. L.; et al. Expanding the Genetic and Clinical Spectrum of SLC25A42-Associated Disorders and Testing of Pantothenic Acid to Improve CoA Level In Vitro. JIMD Rep. 2024, 65 (6), 417–425. 

  14. Fiermonte, G.; Paradies, E.; Todisco, S.; Marobbio, C. M. T.; Palmieri, F. A Novel Member of Solute Carrier Family 25 (SLC25A42) Is a Transporter of Coenzyme A and Adenosine 3',5'-Diphosphate in Human Mitochondria. J. Biol. Chem. 2009, 284 (27), 18152–18159. 

  15. Agrimi, G.; Russo, A.; Scarcia, P.; Palmieri, F. The Human Gene SLC25A17 Encodes a Peroxisomal Transporter of Coenzyme A, FAD and NAD+. Biochem. J. 2012, 443 (1), 241–247. 

  16. Swerdlow, R. D.; Setlow, P. Purification and Characterization of a Bacillus Megaterium Disulfide Reductase Specific for Disulfides Containing Pantethine 4',4''-Diphosphate. J. Bacteriol. 1983, 153 (1), 475–484. 

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