The shikimate pathway is a seven step metabolic route used by bacteria, fungi, and plants for the biosythesis of aromatic amino acids (phenylalanine, tyrosine, and tryptophan).
Cinnamic and p-coumaric acids biosynthesis
In plants, the biosynthesis of all phenylpropanoids begins with the amino acids phenylalanine and tyrosine.
Phenylalanine ammonia-lyase (PAL, a.k.a. phenylalanine/tyrosine ammonia-lyase) is an enzyme responsible for the transformation of L-phenylalanine or tyrosine into trans-cinnamic acid or p-coumaric acid respectively and ammonia.
Trans-cinnamate 4-monooxygenase (cinnamate 4-hydroxylase) is the enzyme responsible for the transformation of trans-cinnamate into 4-hydroxycinnamate (p-coumaric acid). 4-Coumarate-CoA ligase is the enzyme responsible for the transformation of 4-coumarate (p-coumaric acid) into 4-coumaroyl-CoA.
Cinnamyl-alcohol dehydrogenase (CAD), an enzyme responsible for the transformation of cinnamyl alcohol into cinnamaldehyde
Sinapine esterase, an enzyme responsible for the transformation of sinapoylcholine into sinapate (sinapic acid) and choline
Trans-cinnamate 2-monooxygenase, an enzyme responsible for the transformation of trans-cinnamate (cinnamic acid) into 2-hydroxycinnamate
Caffeate O-methyltransferase, an enzyme responsible for the transformation of caffeic acid into ferulic acid
Caffeoyl-CoA O-methyltransferase, an enzyme responsible for the transformation of caffeoyl-CoA into feruloyl-CoA
5-O-(4-coumaroyl)-D-quinate 3'-monooxygenase, an enzyme responsible for the transformation of trans-5-O-(4-coumaroyl)-D-quinate into trans-5-O-caffeoyl-D-quinate
Sinapoylglucose—choline O-sinapoyltransferase, an enzyme responsible for the transformation of 1-O-sinapoyl-beta-D-glucose into sinapoylcholine (sinapine)
Sinapoylglucose—malate O-sinapoyltransferase, an enzyme responsible for the transformation of 1-O-sinapoyl-beta-D-glucose into sinapoyl-(S)-malate
2-coumarate O-beta-glucosyltransferase, an enzyme responsible for the transformation of trans-2-hydroxycinnamate into trans-beta-D-glucosyl-2-hydroxycinnamate
Cinnamoyl-CoA reductase, an enzyme responsible for the production of cinnamoyl-CoA from cinnamaldehyde
Hydroxycinnamate 4-beta-glucosyltransferase, an enzyme responsible for the transformation of p-coumaric acid into 4-O-beta-D-glucosyl-4-hydroxycinnamate
Shikimate O-hydroxycinnamoyltransferase, an enzyme responsible for the transformation of 4-coumaroyl-CoA into 4-coumaroylshikimate
Quinate O-hydroxycinnamoyltransferase, an enzyme responsible for the transformation of feruloyl-CoA into O-feruloylquinate
Sinapate 1-glucosyltransferase, an enzyme responsible for the transformation of sinapate (sinapic acid) into 1-sinapoyl-D-glucose
Coniferyl-alcohol glucosyltransferase, an enzyme responsible for the transformation of coniferyl alcohol into coniferin
Coniferin beta-glucosidase, an enzyme responsible for the transformation of coniferin into coniferol
Pinosylvin synthase, an enzyme responsible for the formation of pinosylvin from cinnamoyl-CoA
Trihydroxystilbene synthase, an enzyme responsible for the production of resveratrol from 4-coumaroyl-CoA
An alternative bacterial ketosynthase-directed stibenoids biosynthesis pathway exists in Photorhabdus bacterial symbionts of Heterorhabditis nematodes, producing 3,5-dihydroxy-4-isopropyl-trans-stilbene for antibiotic purposes.
Scopoletin glucosyltransferase, an enzyme responsible for the transformation of scopoletin into scopolin
4-Coumaroyl-CoA can be combined with malonyl-CoA to yield the true backbone of flavonoids, a group of compounds called chalconoids, which contain two phenyl rings. Naringenin-chalcone synthase is an enzyme that catalyzes the chemical reaction 3 malonyl-CoA + 4-coumaroyl-CoA → 4 CoA + naringenin chalcone + 3 CO2.
Conjugate ring-closure of chalcones results in the familiar form of flavonoids, the three-ringed structure of a flavone.
Caffeate 3,4-dioxygenase is an enzyme that uses 3,4-dihydroxy-trans-cinnamate (caffeic acid) and oxygen to produce 3-(2-carboxyethenyl)-cis,cis-muconate.
