1-Pyrroline-5-carboxylic acid explained

1-Pyrroline-5-carboxylic acid (systematic name 3,4-dihydro-2H-pyrrole-2-carboxylic acid^[1]) 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).^[2]

Biochemistry

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.^{[3] [4] [5]}

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.^{[6] [7]} 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.^[8]

Notes and References

1. Web site: 3,4-Dihydro-2H-pyrrole-2-carboxylic acid. PubChem. pubchem.ncbi.nlm.nih.gov. en. 2020-01-23.
2. 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. Analytical Biochemistry. en. 64. 2. 593–600. 10.1016/0003-2697(75)90472-8. 236687. 0003-2697.
3. Bertolo. Robert F.. Burrin. Douglas G.. 2008-10-01. Comparative Aspects of Tissue Glutamine and Proline Metabolism. The Journal of Nutrition. en. 138. 10. 2032S–2039S. 10.1093/jn/138.10.2032S. 18806120. 0022-3166. free.
4. Qamar. Aarzoo. Mysore. Kirankumar. Senthil-Kumar. Muthappa. 2015. Role of proline and pyrroline-5-carboxylate metabolism in plant defense against invading pathogens. Frontiers in Plant Science. en. 6. 503 . 10.3389/fpls.2015.00503. 4491715. 26217357. 1664-462X. free.
5. Winter. Gudrun. Todd. Christopher D.. Trovato. Maurizio. Forlani. Giuseppe. Funck. Dietmar. 2015. Physiological implications of arginine metabolism in plants. Frontiers in Plant Science. en. 6. 534. 10.3389/fpls.2015.00534. 26284079. 4520006. 1664-462X. free .
6. Liu G, Maunoury C, Kamoun P, Aral B. Oct 1996. 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. 10.1006/geno.1996.0535. 8921385.
7. Web site: Entrez Gene: ALDH18A1 aldehyde dehydrogenase 18 family, member A1.
8. Liu. Li-Kai. Becker. Donald F.. Tanner. John J.. 2017-10-15. Structure, function, and mechanism of proline utilization A (PutA). Archives of Biochemistry and Biophysics. Flavoproteins: Beyond the Classical Paradigms. en. 632. 142–157. 10.1016/j.abb.2017.07.005. 28712849. 5650515. 0003-9861.