Palmitoyl-CoA

Palmitoyl-CoA is an acyl-CoA thioester. It is an "activated" form of palmitic acid and can be transported into the mitochondrial matrix by the carnitine shuttle system (which transports fatty acyl-CoA molecules into the mitochondria), and once inside can participate in beta-oxidation. Alternatively, palmitoyl-CoA is used as a substrate in the biosynthesis of sphingosine (this biosynthetic pathway does not require transfer into the mitochondria).^[1][2]

Palmitoyl-CoA

Names
IUPAC name 3′-O-Phosphonoadenosine 5′-{(3R)-4-[(3-{[2-(hexadecanoylsulfanyl)ethyl]amino}-3-oxopropyl)amino]-3-hydroxy-2,2-dimethyl-4-oxobutyl dihydrogen diphosphate}
Systematic IUPAC name O1-{[(2R,3S,4R,5R)-5-(6-Amino-9H-purin-9-yl)-4-hydroxy-3-(phosphonooxy)oxolan-2-yl]methyl} O3-{(3R)-4-[(3-{[2-(hexadecanoylsulfanyl)ethyl]amino}-3-oxopropyl)amino]-3-hydroxy-2,2-dimethyl-4-oxobutyl} dihydrogen diphosphate
Identifiers
CAS Number	1763-10-6 Y
3D model (JSmol)	Interactive image
ChemSpider	559149 N
ECHA InfoCard	100.015.616
KEGG	C00154 N
MeSH	Palmitoyl+Coenzyme+A
PubChem CID	644109
CompTox Dashboard (EPA)	DTXSID701027137
InChI InChI=1S/C37H66N7O17P3S/c1-4-5-6-7-8-9-10-11-12-13-14-15-16-17-28(46)65-21-20-39-27(45)18-19-40-35(49)32(48)37(2,3)23-58-64(55,56)61-63(53,54)57-22-26-31(60-62(50,51)52)30(47)36(59-26)44-25-43-29-33(38)41-24-42-34(29)44/h24-26,30-32,36,47-48H,4-23H2,1-3H3,(H,39,45)(H,40,49)(H,53,54)(H,55,56)(H2,38,41,42)(H2,50,51,52)/t26-,30-,31-,32+,36-/m1/s1 N Key: MNBKLUUYKPBKDU-BBECNAHFSA-N N InChI=1/C37H66N7O17P3S/c1-4-5-6-7-8-9-10-11-12-13-14-15-16-17-28(46)65-21-20-39-27(45)18-19-40-35(49)32(48)37(2,3)23-58-64(55,56)61-63(53,54)57-22-26-31(60-62(50,51)52)30(47)36(59-26)44-25-43-29-33(38)41-24-42-34(29)44/h24-26,30-32,36,47-48H,4-23H2,1-3H3,(H,39,45)(H,40,49)(H,53,54)(H,55,56)(H2,38,41,42)(H2,50,51,52)/t26-,30-,31-,32+,36-/m1/s1 Key: MNBKLUUYKPBKDU-BBECNAHFBL
SMILES CCCCCCCCCCCCCCCC(=O)SCCNC(=O)CCNC(=O)[C@@H](C(C)(C)COP(=O)(O)OP(=O)(O)OC[C@@H]1[C@H]([C@H]([C@@H](O1)n2cnc3c2ncnc3N)O)OP(=O)(O)O)O
Properties
Chemical formula	C37H66N7O17P3S
Molar mass	1005.95 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Biosynthesis

Palmitoyl CoA formed from palmitic acid, in the reaction below.^[3]

Palmitate + CoA-SH + ATP → Palmitoyl-CoA + AMP + Pyrophosphate

This reaction is often referred to as the "activation" of a fatty acid. The activation is catalyzed by palmitoyl-coenzyme A synthetase and the reaction proceeds through a two step mechanism, in which palmitoyl-AMP is an intermediate.^[4] The reaction is driven to completion by the exergonic hydrolysis of pyrophosphate.^[3]

The activation of fatty acids occurs in the cytosol and beta-oxidation occurs in the mitochondria. However, long chain fatty acyl-CoA cannot cross the mitochondrial membrane. If palmitoyl-CoA is to enter the mitochondria, it must react with carnitine in order to be transported across:

Palmitoyl-CoA + Carnitine ⇌ Palmitoyl-Carnitine + CoA-SH

This transesterification reaction is catalyzed by carnitine palmitoyl transferase.^[5] Palmitoyl-Carnitine may translocate across the membrane, and once on matrix side, the reaction proceeds in reverse as CoA-SH is recombined with palmitoyl-CoA, and released. Unattached carnitine is then shuttled back to the cytosolic side of mitochondrial membrane.

Beta-oxidation

Once inside the mitochondrial matrix, palmitoyl-CoA may undergo β-oxidation. The full oxidation of palmitic acid (or palmitoyl-CoA) results in 8 acetyl-CoA's, 7 NADH, 7 H⁺, and 7 FADH₂.^[6] The full reaction is below:

Palmitoyl-CoA + 7 CoA-SH + 7 NAD⁺ + 7 FAD → 8 Acetyl-CoA + 7 NADH + 7 H⁺ + 7 FADH₂

Sphingolipid biosynthesis

Palmitoyl-CoA is also the starting substrate, along with serine, for sphingolipid biosynthesis. Palmitoyl CoA and serine participate in a condensation reaction catalyzed by serine C-palmitoyltransferase (SPT), in which 3-ketosphinganine is formed. These reactions occur in the cytosol.^[7]

Sphingosine synthesis

Additional images

• 
  Synthesis
• 
  Palmitic acid
• 
  Coenzyme A

See also

• Coenzyme A (CoA)

References

1. Brady, R.N.; DiMari, S.J.; Snell, E.E. (1969). "Biosynthesis of sphingolipid bases. 3. Isolation and characterization of ketonic intermediates in the synthesis of sphingosine and dihydrosphingosine by cell-free extracts of Hansenula ciferri". J. Biol. Chem. 244 (2): 491–496. doi:10.1016/S0021-9258(18)94455-8. PMID 4388074.
2. Stoffel, W.; Le Kim, D.; Sticht, G. (1968). "Biosynthesis of dihydrosphingosine in vitro". Hoppe-Seyler's Z. Physiol. Chem. 349 (5): 664–670. doi:10.1515/bchm2.1968.349.1.664. PMID 4386961.
3. Voet, Donald; Voet, Judith G.; Pratt, Charlotte W. (2016-02-29). Fundamentals of Biochemistry: Life at the Molecular Level. John Wiley & Sons. ISBN 978-1-118-91840-1.
4. Bar–Tana, J.; Rose, G.; Brandes, R.; Shapiro, B. (1973-02-01). "Palmitoyl-coenzyme A synthetase. Mechanism of reaction". Biochemical Journal. 131 (2): 199–209. doi:10.1042/bj1310199. ISSN 0264-6021. PMC 1177459. PMID 4722436.
5. Sharma, R. (2013), "Biochemical Mechanisms of Fatty Liver and Bioactive Foods", Bioactive Food as Dietary Interventions for Liver and Gastrointestinal Disease, Elsevier, pp. 709–741, doi:10.1016/b978-0-12-397154-8.00041-5, ISBN 978-0-12-397154-8
6. Kamel, Kamel S.; Halperin, Mitchell L. (2017), "Ketoacidosis", Fluid, Electrolyte and Acid-Base Physiology, Elsevier, pp. 99–139, doi:10.1016/b978-0-323-35515-5.00005-1, ISBN 978-0-323-35515-5
7. Michel, Christoph; van Echten-Deckert, Gerhild (1997-10-20). "Conversion of dihydroceramide to ceramide occurs at the cytosolic face of the endoplasmic reticulum". FEBS Letters. 416 (2): 153–155. Bibcode:1997FEBSL.416..153M. doi:10.1016/s0014-5793(97)01187-3. ISSN 0014-5793. PMID 9369202. S2CID 467943.