Flavonoid biosynthesis
Encyclopedia
Flavonoids are synthesized by the phenylpropanoid
metabolic pathway
in which the amino acid
phenylalanine
is used to produce 4-coumaroyl-CoA. This can be combined with malonyl-CoA
to yield the true backbone of flavonoids, a group of compounds called chalcones, which contain two phenyl rings. Conjugate ring-closure of chalcones results in the familiar form of flavonoids, the three-ringed structure of a flavone. The metabolic pathway continues through a series of enzymatic modifications to yield flavanone
s → dihydroflavonols → anthocyanin
s. Along this pathway, many products can be formed, including the flavonols, flavan-3-ol
s, proanthocyanidin
s (tannins) and a host of other various polyphenolics.
Flavanoids can possess chiral
carbons. Methods of analysis should take this element into account especially regarding bioactivity or enzyme stereospecificity
.
The biosynthesis
of flavonoid
s involves several enzyme
s.
Phenylpropanoid
The phenylpropanoids are a diverse family of organic compounds that are synthesized by plants from the amino acid phenylalanine. Their name is derived from the six-carbon, aromatic phenyl group and the three-carbon propene tail of cinnamic acid, which is synthesized from phenylalanine in the first...
metabolic pathway
Metabolic pathway
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...
in which the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
phenylalanine
Phenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
is used to produce 4-coumaroyl-CoA. This can be combined with malonyl-CoA
Malonyl-CoA
Malonyl-CoA is a coenzyme A derivative.-Functions:It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis....
to yield the true backbone of flavonoids, a group of compounds called chalcones, which contain two phenyl rings. Conjugate ring-closure of chalcones results in the familiar form of flavonoids, the three-ringed structure of a flavone. The metabolic pathway continues through a series of enzymatic modifications to yield flavanone
Flavanone
The flavanones are a type of flavonoids. They are generally glycosylated by a disaccharide at position seven to give flavanone glycosides.-List of flavanones:* Butin* Eriodictyol* Hesperetin* Hesperidin* Homoeriodictyol* Isosakuranetin* Naringenin...
s → dihydroflavonols → anthocyanin
Anthocyanin
Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...
s. Along this pathway, many products can be formed, including the flavonols, flavan-3-ol
Flavan-3-ol
Flavan-3-ols are a class of flavonoids that use the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. These compounds include the catechins and the catechin gallates....
s, proanthocyanidin
Proanthocyanidin
Proanthocyanidins, also known as OPCs or condensed tannins, are a subgroup of the flavonoid class of polyphenols...
s (tannins) and a host of other various polyphenolics.
Flavanoids can possess chiral
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
carbons. Methods of analysis should take this element into account especially regarding bioactivity or enzyme stereospecificity
Stereospecificity
In chemistry, stereospecificity is the property of a reaction mechanism that leads to different stereoisomeric reaction products from different stereoisomeric reactants, or which operates on only one of the stereoisomers."Overlap Control of Carbanionoid Reactions. I. Stereoselectivity in Alkaline...
.
The biosynthesis
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
of flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
s involves several enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s.
- Dihydrokaempferol 4-reductaseDihydrokaempferol 4-reductaseIn enzymology, a dihydrokaempferol 4-reductase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are cis-3,4-leucopelargonidin and NADP+, whereas its 3 products are -dihydrokaempferol, NADPH, and H+....
- Flavanone 4-reductaseFlavanone 4-reductaseIn enzymology, a flavanone 4-reductase is an enzyme that catalyzes the chemical reaction-flavan-4-ol + NADP+ \rightleftharpoons -flavanone + NADPH + H+...
- Anthocyanidin reductaseAnthocyanidin reductaseIn enzymology, an anthocyanidin reductase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are flavan-3-ol, NAD+, and NADP+, whereas its 4 products are anthocyanidin, NADH, NADPH, and H+....
- Flavanone 3-dioxygenaseFlavanone 3-dioxygenaseIn enzymology, a flavanone 3-dioxygenase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are flavanone, 2-oxoglutarate, and O2, whereas its 3 products are dihydroflavonol, succinate, and CO2....
- Flavone synthaseFlavone synthaseIn enzymology, a flavone synthase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are flavanone, 2-oxoglutarate, and O2, whereas its 4 products are flavone, succinate, CO2, and H2O....
- Flavonoid 3'-monooxygenaseFlavonoid 3'-monooxygenaseIn enzymology, a flavonoid 3'-monooxygenase is an enzyme that catalyzes the chemical reactionThe 4 substrates of this enzyme are flavonoid, NADPH, H+, and O2, whereas its 3 products are 3'-hydroxyflavonoid, NADP+, and H2O....
- Flavonol synthaseFlavonol synthaseIn enzymology, a flavonol synthase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are dihydroflavonol, 2-oxoglutarate, and O2, whereas its 4 products are flavonol, succinate, CO2, and H2O....
- Leucocyanidin oxygenaseLeucocyanidin oxygenaseIn enzymology, a leucocyanidin oxygenase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are leucocyanidin, 2-oxoglutarate, and O2, whereas its 5 products are cis-dihydroquercetin, trans-dihydroquercetin, succinate, CO2, and H2O.This enzyme belongs to the family of...
- Leucoanthocyanidin reductaseLeucoanthocyanidin reductaseIn enzymology, a leucoanthocyanidin reductase is an enzyme that catalyzes the chemical reaction-catechin + NADP+ + H2O \rightleftharpoons 2,3-trans-3,4-cis-leucocyanidin + NADPH + H+...
- Chalcone isomeraseChalcone isomeraseIn enzymology, a chalcone isomerase is an enzyme that catalyzes the chemical reactionHence, this enzyme has one substrate, a chalcone, and one product, a flavanone....
- Naringenin-chalcone synthaseNaringenin-chalcone synthaseIn enzymology, a naringenin-chalcone synthase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are malonyl-CoA and 4-coumaroyl-CoA, whereas its 3 products are CoA, naringenin chalcone, and CO2....
Methylation
- Apigenin 4'-O-methyltransferaseApigenin 4'-O-methyltransferaseIn enzymology, an apigenin 4'-O-methyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are S-adenosyl methionine and 5,7,4'-trihydroxyflavone , whereas its two products are S-adenosylhomocysteine and 4'-methoxy-5,7-dihydroxyflavone .This enzyme...
- Luteolin O-methyltransferaseLuteolin O-methyltransferaseIn enzymology, a luteolin O-methyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are S-adenosyl methionine and 5,7,3',4'-tetrahydroxyflavone , whereas its two products are S-adenosylhomocysteine and 5,7,4'-trihydroxy-3'-methoxyflavone.This...
- Quercetin 3-O-methyltransferaseQuercetin 3-O-methyltransferaseIn enzymology, a quercetin 3-O-methyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are S-adenosyl methionine and 3,5,7,3',4'-pentahydroxyflavone, whereas its two products are S-adenosylhomocysteine and...
Glycosylation
- Anthocyanidin 3-O-glucosyltransferaseAnthocyanidin 3-O-glucosyltransferaseIn enzymology, an anthocyanidin 3-O-glucosyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are UDP-D-glucose and anthocyanidin, whereas its two products are UDP and anthocyanidin-3-O-beta-D-glucoside....
- Flavone 7-O-beta-glucosyltransferaseFlavone 7-O-beta-glucosyltransferaseIn enzymology, a flavone 7-O-beta-glucosyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are UDP-glucose and 5,7,3',4'-tetrahydroxyflavone , whereas its two products are UDP and 7-O-beta-D-glucosyl-5,7,3',4'-tetrahydroxyflavone .This enzyme...
- Flavone apiosyltransferaseFlavone apiosyltransferaseIn enzymology, a flavone apiosyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are UDP-apiose and 5,7,4'-trihydroxyflavone 7-O-beta-D-glucoside, whereas its 3 products are UDP, 5,7,4'-trihydroxyflavone , and...
- Flavonol-3-O-glucoside L-rhamnosyltransferaseFlavonol-3-O-glucoside L-rhamnosyltransferaseIn enzymology, a flavonol-3-O-glucoside L-rhamnosyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are UDP-L-rhamnose and flavonol 3-O-D-glucoside, whereas its two products are UDP and flavonol 3-O-[beta-L-rhamnosyl--beta-D-glucoside].This...
- Flavonol 3-O-glucosyltransferaseFlavonol 3-O-glucosyltransferaseIn enzymology, a flavonol 3-O-glucosyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are UDP-glucose and flavonol, whereas its two products are UDP and flavonol 3-O-beta-D-glucoside....