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Pterin - Pterin.svg
IUPAC names
(one of five tautomers)
Other names
3D model (JSmol)
ECHA InfoCard 100.017.091 Edit this at Wikidata
  • InChI=1S/C6H5N5O/c7-6-10-4-3(5(12)11-6)8-1-2-9-4/h1-2H,(H3,7,9,10,11,12) checkY
  • InChI=1/C6H5N5O/c7-6-10-4-3(5(12)11-6)8-1-2-9-4/h1-2H,(H3,7,9,10,11,12)
  • O=C2\N=C(/Nc1nccnc12)N
Molar mass 163.137
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Pterin is a heterocyclic compound composed of a pteridine ring system, with a "keto group" (a lactam) and an amino group on positions 4 and 2 respectively. It is structurally related to the parent bicyclic heterocycle called pteridine. Pterins, as a group, are compounds related to pterin with additional substituents. Pterin itself is of no biological significance.

Pterins were first discovered in the pigments of butterfly wings[1] (hence the origin of their name, from the Greek pteron (πτερόν),[2] wing) and perform many roles in coloration in the biological world.


The enzyme is found in both prokaryotes and eukaryotes. Two intermediates in this conversion are 7,8-dihydroneopterin triphosphate and 6-pyruvoyl-5,6,7,8-tetrahydropterin. These conversions are mediated by three enzymes, the first being GTP cyclohydrolase I (GTPCH-1, FolE), which expands the imidazole ring in GTP by one carbon. The next enzyme is (6-pyruvoyltetrahydropterin synthase, which removed the phosphate and produces the diketone (pyruvoyl) substituent. The final stage is mediated by sepiapterin reductase.[3]

step in biosynthesis of dihydroneopterin from GTP.

Pterin cofactors[edit]

Pterin derivatives are common cofactors in all domains of life.


One important family of pterin derivatives are Folates. Folates are pterins that contain p-aminobenzoic acid connected to the methyl group at position 6 of the pteridine ring system (known as pteroic acid) conjugated with one or more L-glutamates. They participate in numerous biological group transfer reactions. Folate-dependent biosynthetic reactions include the transfer of methyl groups from 5-methyltetrahydrofolate to homocysteine to form L-methionine, and the transfer of formyl groups from 10-formyltetrahydrofolate to L-methionine to form N-formylmethionine in initiator tRNAs. Folates are also essential for the biosynthesis of purines and one pyrimidine.

Substituted pteridines are intermediates in the biosynthesis of dihydrofolic acid in many microorganisms.[4] The enzyme dihydropteroate synthetase converts pteridine and 4-aminobenzoic acid to dihydrofolic acid in the presence of glutamate. The enzyme dihydropteroate synthetase is inhibited by sulfonamide antibiotics.


Moco biosynthetic pathway in bacteria and humans. The human enzymes are indicated in parenthesis.[5]

Molybdopterin is a cofactor found in virtually all molybdenum and tungsten-containing proteins.[6] It binds molybdenum to yield redox cofactors involved in biological hydroxylations, reduction of nitrate, and respiratory oxidation.[7]

Molybdopterin biosynthesis does not use the conventional GTPCH-1 pathway. It occurs in four steps:[5]

  1. the radical-mediated cyclization of nucleotide, guanosine 5'-triphosphate (GTP), to (8S)‑3 ́,8‐cyclo‑7,8‑dihydroguanosine 5 ́‑triphosphate (3 ́,8‑cH2GTP),
  2. the formation of cyclic pyranopterin monophosphate (cPMP) from the 3 ́,8‑cH2GTP,
  3. the conversion of cPMP into molybdopterin (MPT),
  4. the insertion of molybdate into MPT to form Moco (molybdenum cofactor).


Tetrahydrobiopterin, the major unconjugated pterin in vertebrates, is involved in three families of enzymes that effect hydroxylation. The aromatic amino acid hydroxylases include phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylases. They are involved in the synthesis of neurotransmitters catecholamine and serotonin. Tetrahydrobiopterin is also required for the functioning of alkylglycerol monooxygenase, whereby monoalkylglycerols are broken down to glycerol and an aldehyde. In the synthesis of nitric oxide the pterin-dependent nitric oxide synthase converts arginine to N-hydroxy derivative, which in turn releases NO.[8]

Other pterins[edit]

Cycle for methanogenesis, showing intermediates.

Tetrahydromethanopterin is a cofactor in methanogenesis, which is a metabolism adopted by many organisms, as a form of anaerobic respiration.[9] It caries the C1 substrate in the course of the formation or production of methane.

Pterin pigments[edit]

The wings of the orange tip butterfly are colored by orange pterin-containing pigments.[10]

Cyanopterin[11] is a glycosylated version of pteridine of unknown function in cyanobacteria.

See also[edit]


  1. ^ Wijnen, B.; Leertouwer, H. L.; Stavenga, D. G. (2007). "Colors and pterin pigmentation of pierid butterfly wings" (PDF). Journal of Insect Physiology. 53 (12): 1206–17. doi:10.1016/j.jinsphys.2007.06.016. PMID 17669418. S2CID 13787442.
  2. ^ πτερόν. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
  3. ^ Werner, Ernst R.; Blau, Nenad; Thöny, Beat (2011). "Tetrahydrobiopterin: Biochemistry and pathophysiology". Biochemical Journal. 438 (3): 397–414. doi:10.1042/BJ20110293.
  4. ^ Voet, D.; Voet, J.G. (2004). Biochemistry (3rd ed.). John Wiley & Sons. ISBN 0-471-39223-5
  5. ^ a b Schwarz, G. & Mendel, R. R. (2006). "Molybdenum cofactor biosynthesis and molybdenum enzymes". Annual Review of Plant Biology. 57: 623–647. doi:10.1146/annurev.arplant.57.032905.105437. PMID 16669776.
  6. ^ Feirer, Nathan; Fuqua, Clay (2017-01-01). "Pterin function in bacteria". Pteridines. 28 (1): 23–36. doi:10.1515/pterid-2016-0012. ISSN 2195-4720.
  7. ^ Schwarz, Guenter; Mendel, Ralf R.; Ribbe, Markus W. (2009). "Molybdenum cofactors, enzymes and pathways". Nature. 460 (7257): 839–847. Bibcode:2009Natur.460..839S. doi:10.1038/nature08302. PMID 19675644. S2CID 205217953.{{cite journal}}: CS1 maint: uses authors parameter (link)
  8. ^ Werner, Ernst R. (2013-01-01). "Three classes of tetrahydrobiopterin-dependent enzymes". Pteridines. 24 (1): 7–11. doi:10.1515/pterid-2013-0003. ISSN 2195-4720. S2CID 87712042.
  9. ^ Thauer, R. K. (1998). "Biochemistry of Methanogenesis: a Tribute to Marjory Stephenson". Microbiology. 144: 2377–2406. doi:10.1099/00221287-144-9-2377. PMID 9782487.
  10. ^ B. Wijnen, H. L. Leertouwer, D. G.Stavenga (2007). "Colors and pterin pigmentation of pierid butterfly wings" (PDF). Journal of Insect Physiology. 53 (12): 1206–1217. doi:10.1016/j.jinsphys.2007.06.016. PMID 17669418. S2CID 13787442.{{cite journal}}: CS1 maint: uses authors parameter (link)
  11. ^ Lee, Hee Woo; Oh, Chang Ho; Geyer, Armin; Pfleiderer, Wolfgang; Park, Young Shik (1999-01-27). "Characterization of a novel unconjugated pteridine glycoside, cyanopterin, in Synechocystis sp. PCC 6803". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1410 (1): 61–70. doi:10.1016/S0005-2728(98)00175-3. ISSN 0005-2728. PMID 10076015.

External links[edit]