Chemistry:1-Pyrroline-5-carboxylic acid

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1-Pyrroline-5-carboxylic acid
Delta-1-pyrroline-5-carboxylic acid.svg
Preferred IUPAC name
3,4-Dihydro-2H-pyrrole-2-carboxylic acid
Other names
1-Pyrroline-5-carboxylic acid
δ-1-Pyrroline-5-carboxylic acid
3D model (JSmol)
MeSH Delta-1-pyrroline-5-carboxylate
Molar mass 113.115 g/mol
Acidity (pKa) 1.82/6.07[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

1-Pyrroline-5-carboxylic acid (systematic name 3,4-dihydro-2H-pyrrole-2-carboxylic acid[2]) is a cyclic imino acid. Its conjugate base and anion is 1-pyrroline-5-carboxylate (P5C). In solution, P5C is in spontaneous equilibrium with glutamate-5-semialdhyde (GSA).[3] The stereoisomer (S)-1-pyrroline-5-carboxylate (also referred to as L-P5C) is an intermediate metabolite in the biosynthesis and degradation of proline and arginine.[4][5][6]

In prokaryotic proline biosynthesis, GSA is synthesized from γ-glutamyl phosphate by the enzyme γ-glutamyl phosphate reductase. In most eukaryotes, GSA is synthesised from the amino acid glutamate by the bifunctional enzyme 1-pyrroline-5-carboxylate synthase (P5CS). The human P5CS is encoded by the ALDH18A1 gene.[7][8] The enzyme pyrroline-5-carboxylate reductase converts P5C into proline

In proline degradation, the enzyme proline dehydrogenase produces P5C from proline, and the enzyme 1-pyrroline-5-carboxylate dehydrogenase converts GSA to glutamate. In many prokaryotes, proline dehydrogenase and P5C dehydrogenase form a bifunctional enzyme that prevents the release of P5C during proline degradation.[9] In arginine degradation, the enzyme ornithine-δ-aminotransferase mediates the transamination between ornithine and a 2-oxo acid (typically α-ketoglutarate) to form P5C and an L-amino acid (typically glutamate). Under specific conditions, P5C may also be used for arginine biosynthesis via the reverse reaction of ornithine-δ-aminotransferase.[4]


  1. "computed by Chemicalize from ChemAxon". 
  2. PubChem. "3,4-Dihydro-2H-pyrrole-2-carboxylic acid" (in en). 
  3. Heacock, Anne M.; Williams, Irene H.; Frank, Leonard H.; Adams, Elijah (1975-04-01). "Δ1-Pyrroline-5-carboxylate and Δ1-pyrroline-3-hydroxy-5-carboxylate: Chromatography on the amino acid analyzer" (in en). Analytical Biochemistry 64 (2): 593–600. doi:10.1016/0003-2697(75)90472-8. ISSN 0003-2697. PMID 236687. 
  4. 4.0 4.1 Bertolo, Robert F.; Burrin, Douglas G. (2008-10-01). "Comparative Aspects of Tissue Glutamine and Proline Metabolism" (in en). The Journal of Nutrition 138 (10): 2032S–2039S. doi:10.1093/jn/138.10.2032S. ISSN 0022-3166. PMID 18806120. 
  5. Qamar, Aarzoo; Mysore, Kirankumar; Senthil-Kumar, Muthappa (2015). "Role of proline and pyrroline-5-carboxylate metabolism in plant defense against invading pathogens" (in en). Frontiers in Plant Science 6: 503. doi:10.3389/fpls.2015.00503. ISSN 1664-462X. PMID 26217357. 
  6. Winter, Gudrun; Todd, Christopher D.; Trovato, Maurizio; Forlani, Giuseppe; Funck, Dietmar (2015). "Physiological implications of arginine metabolism in plants" (in en). Frontiers in Plant Science 6: 534. doi:10.3389/fpls.2015.00534. ISSN 1664-462X. PMID 26284079. 
  7. "Assignment of the human gene encoding the delta 1-pyrroline-5-carboxylate synthetase (P5CS) to 10q24.3 by in situ hybridization". Genomics 37 (1): 145–6. Oct 1996. doi:10.1006/geno.1996.0535. PMID 8921385. 
  8. "Entrez Gene: ALDH18A1 aldehyde dehydrogenase 18 family, member A1". 
  9. Liu, Li-Kai; Becker, Donald F.; Tanner, John J. (2017-10-15). "Structure, function, and mechanism of proline utilization A (PutA)" (in en). Archives of Biochemistry and Biophysics. Flavoproteins: Beyond the Classical Paradigms 632: 142–157. doi:10.1016/ ISSN 0003-9861. PMID 28712849.