In plants, all phenylpropanoids are derived from the amino acids
phenylalanine and
tyrosine.
Phenylalanine ammonia-lyase (PAL, a.k.a. phenylalanine/tyrosine ammonia-lyase) is an enzyme that transforms L-
phenylalanine and
tyrosine into trans-
cinnamic acid and
p-coumaric acid, respectively.
Trans-cinnamate 4-monooxygenase (cinnamate 4-hydroxylase) is the enzyme that transforms trans-cinnamate into 4-hydroxycinnamate (
p-coumaric acid).
4-Coumarate-CoA ligase is the enzyme that transforms 4-coumarate (
p-coumaric acid) into
4-coumaroyl-CoA.
Enzymes associated with biosynthesis of hydroxycinnamic acids •
Cinnamyl-alcohol dehydrogenase (CAD), an enzyme that transforms
cinnamyl alcohol into
cinnamaldehyde •
Sinapine esterase, an enzyme that transforms
sinapoylcholine into sinapate (
sinapic acid) and
choline •
Trans-cinnamate 2-monooxygenase, an enzyme that transforms trans-cinnamate (
cinnamic acid) into
2-hydroxycinnamate •
Caffeate O-methyltransferase, an enzyme that transforms
caffeic acid into
ferulic acid •
Caffeoyl-CoA O-methyltransferase, an enzyme that transforms
caffeoyl-CoA into
feruloyl-CoA •
5-O-(4-coumaroyl)-D-quinate 3'-monooxygenase, an enzyme that transforms
trans-5-O-(4-coumaroyl)-D-quinate into
trans-5-O-caffeoyl-D-quinate •
Sinapoylglucose—choline O-sinapoyltransferase, an enzyme that transforms
1-O-sinapoyl-beta-D-glucose into sinapoylcholine (
sinapine) •
Sinapoylglucose—malate O-sinapoyltransferase, an enzyme that transforms
1-O-sinapoyl-beta-D-glucose into
sinapoyl-(S)-malate •
Cinnamoyl-CoA reductase, an enzyme that transforms
cinnamoyl-CoA from
cinnamaldehyde Conjugation enzymes These enzymes
conjugate phenylpropanoids to other molecules. •
2-coumarate O-beta-glucosyltransferase, the enzyme that transforms
trans-2-hydroxycinnamate into
trans-beta-D-glucosyl-2-hydroxycinnamate •
Hydroxycinnamate 4-beta-glucosyltransferase, the enzyme that transforms
p-coumaric acid into
4-O-beta-D-glucosyl-4-hydroxycinnamate •
Shikimate O-hydroxycinnamoyltransferase, the enzyme that transforms
4-coumaroyl-CoA into
4-coumaroylshikimate •
Quinate O-hydroxycinnamoyltransferase, the enzyme that transforms
feruloyl-CoA into
O-feruloylquinate •
Sinapate 1-glucosyltransferase, the enzyme that transforms sinapate (
sinapic acid) into
1-sinapoyl-D-glucose •
Coniferyl-alcohol glucosyltransferase, the enzyme that transforms
coniferyl alcohol into
coniferin Deconjugation enzymes •
Coniferin beta-glucosidase, in the
glucosidase that transforms
coniferin into
coniferol Stilbenoids biosynthesis •
Pinosylvin synthase, an enzyme that transforms
pinosylvin from
cinnamoyl-CoA •
Trihydroxystilbene synthase, an enzyme that transforms
4-coumaroyl-CoA to
resveratrol. An alternative bacterial
ketosynthase-directed
stilbenoids biosynthesis pathway exists in
Photorhabdus bacterial symbionts of
Heterorhabditis nematodes, producing
3,5-dihydroxy-4-isopropyl-trans-stilbene for antibiotic purposes. ===
Coumarins biosynthesis === •
Scopoletin glucosyltransferase, the enzyme that transforms
scopoletin into
scopolin Chalcones biosynthesis 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 following conversion: :3-malonyl-CoA + 4-coumaroyl-CoA → 4 CoA +
naringenin chalcone + 3 CO2
Flavonoids biosynthesis Conjugate ring-closure of chalcones results in the familiar form of
flavonoids, the three-ringed structure of a
flavone. == Biodegradation ==