Pterin
Encyclopedia
Pterin is a heterocyclic compound composed of a pteridine
ring system, with a keto group and an amino group on positions 4 and 2 respectively. Several tautomer
s of pterin exist and are shown below.
Derivatives of pterin include pterins and folates.
Pterins, as a group, are compounds that are derivatives of the basic pterin structure, described in the beginning, with additional functional groups attached to the pyrazine
subring. Pterins were first discovered in the pigments of butterfly
wings (hence the origin of their name, from the Greek pteron (πτερόν), wing) and perform many roles in coloration in the biological world. Pterins also function as cofactor
s in enzyme catalysis
.
Folates are “conjugated” pterins that contain p-aminobenzoic acid and L-glutamates connected to the methyl group at position 6 of the pteridine ring system. They are critical compounds in a large number of biological group transfer reactions. These folate-dependent biosynthetic reactions include the transfer of methyl group
s 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.
(GTP); the enzyme that controls the conversion of GTP to pterin, GTP cyclohydrolase I
, is found in both prokaryote
s and eukaryote
s.
, the major unconjugated pteridine in vertebrates, is a co-factor in the hydroxylation of aromatic compounds and synthesis of nitric oxide. Molybdopterin
is a substituted pteridine that binds molybdenum
to give redox enzymes involved in biological hydroxylations, reduction of nitrate, and respiratory oxidation. Tetrahydromethanopterin
is used in methanogenic organisms. Cyanopterin is a glycosylated version of pteridine of unknown function in cyanobacteria.
Pteridine
Pteridine is a chemical compound composed of fused pyrimidine and pyrazine rings. A pteridine is also a group of heterocyclic compounds containing a wide variety of substitutions on this structure. Pterins and flavins are classes of substituted pteridines that have important biological...
ring system, with a keto group and an amino group on positions 4 and 2 respectively. Several tautomer
Tautomer
Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. This reaction commonly results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond...
s of pterin exist and are shown below.
Derivatives of pterin include pterins and folates.
Pterins, as a group, are compounds that are derivatives of the basic pterin structure, described in the beginning, with additional functional groups attached to the pyrazine
Pyrazine
Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2.Pyrazine is a symmetrical molecule with point group D2h. Derivatives like phenazine are well known for their antitumor, antibiotic and diuretic activity. Pyrazine is less basic in nature than pyridine, pyridazine...
subring. Pterins were first discovered in the pigments of butterfly
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
wings (hence the origin of their name, from the Greek pteron (πτερόν), wing) and perform many roles in coloration in the biological world. Pterins also function as cofactor
Cofactor (biochemistry)
A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....
s in enzyme catalysis
Enzyme catalysis
Enzyme catalysis is the catalysis of chemical reactions by specialized proteins known as enzymes. Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalysed reactions....
.
Folates are “conjugated” pterins that contain p-aminobenzoic acid and L-glutamates connected to the methyl group at position 6 of the pteridine ring system. They are critical compounds in a large number of biological group transfer reactions. These folate-dependent biosynthetic reactions include the transfer of methyl group
Methyl group
Methyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...
s from 5-methyltetrahydrofolate
5-Methyltetrahydrofolate
Levomefolic acid or metafolin is the natural, active form of folic acid used at the cellular level for DNA reproduction, the cysteine cycle and the regulation of homocysteine among other functions. The un-methylated form, folic acid , is a synthetic form of folate found in nutritional supplements...
to homocysteine
Homocysteine
Homocysteine is a non-protein amino acid with the formula HSCH2CH2CHCO2H. It is a homologue of the amino acid cysteine, differing by an additional methylene group. It is biosynthesized from methionine by the removal of its terminal Cε methyl group...
to form L-methionine
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
, and the transfer of formyl groups from 10-formyltetrahydrofolate to L-methionine
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
to form N-formylmethionine
N-Formylmethionine
N-Formylmethionine is a proteinogenic amino acid found in Bacteria and related Prokaryotic organelles. It is a derivative of the amino acid methionine in which a formyl group has been added to the amino group...
in initiator tRNAs.
Biosynthesis
The biosynthesis of pterins begins with the molecule guanosine triphosphateGuanosine triphosphate
Guanosine-5'-triphosphate is a purine nucleoside triphosphate. It can act as a substrate for the synthesis of RNA during the transcription process...
(GTP); the enzyme that controls the conversion of GTP to pterin, GTP cyclohydrolase I
GTP cyclohydrolase I
GTP cyclohydrolase I is a member of the GTP cyclohydrolase family of enzymes. GTPCH is part of the folate and biopterin biosynthesis pathways. It is responsible for the hydrolysis of guanosine triphosphate to form 7,8-dihydroneopterin 3'-triphosphate .GTPCH is encoded by the gene GCH1...
, is found in both prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...
s and eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
s.
Other pterins
Pterin can exist in many different forms in nature depending on its function. TetrahydrobiopterinTetrahydrobiopterin
Tetrahydrobiopterin or sapropterin is a naturally occurring essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin , melatonin, dopamine, norepinephrine ,...
, the major unconjugated pteridine in vertebrates, is a co-factor in the hydroxylation of aromatic compounds and synthesis of nitric oxide. Molybdopterin
Molybdopterin
Molybdopterins, when reacted with molybdenum or tungsten in the form of molybdate or tungstate, are a class of cofactors found in most molybdenum and all tungsten enzymes...
is a substituted pteridine that binds molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
to give redox enzymes involved in biological hydroxylations, reduction of nitrate, and respiratory oxidation. Tetrahydromethanopterin
Tetrahydromethanopterin
Tetrahydromethanopterin is a coenzyme in methanogenesis. It is the carrier of the C1 group as it is reduced to the methyl level, before transferring to the coenzyme M....
is used in methanogenic organisms. Cyanopterin is a glycosylated version of pteridine of unknown function in cyanobacteria.
See also
- PteridinePteridinePteridine is a chemical compound composed of fused pyrimidine and pyrazine rings. A pteridine is also a group of heterocyclic compounds containing a wide variety of substitutions on this structure. Pterins and flavins are classes of substituted pteridines that have important biological...
- TetrahydrobiopterinTetrahydrobiopterinTetrahydrobiopterin or sapropterin is a naturally occurring essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin , melatonin, dopamine, norepinephrine ,...
- MolybdopterinMolybdopterinMolybdopterins, when reacted with molybdenum or tungsten in the form of molybdate or tungstate, are a class of cofactors found in most molybdenum and all tungsten enzymes...
- Cyanopterin
- TetrahydromethanopterinTetrahydromethanopterinTetrahydromethanopterin is a coenzyme in methanogenesis. It is the carrier of the C1 group as it is reduced to the methyl level, before transferring to the coenzyme M....
- Folic acidFolic acidFolic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...