Phenylpropanoids metabolism

The biosynthesis of phenylpropanoids involves a number of enzymes.

From amino acids to cinnamates

In plants, all phenylpropanoids are derived from the amino acids phenylalanine and tyrosine.

, respectively.

Enzymes associated with biosynthesis of hydroxycinnamic acids

• Cinnamyl-alcohol dehydrogenase (CAD), an enzyme that transforms cinnamyl alcohol into cinnamaldehyde
• sinapic acid) and choline
• 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

phenylpropanoids to other molecules.

• trans-2-hydroxycinnamate into trans-beta-D-glucosyl-2-hydroxycinnamate
• 4-O-beta-D-glucosyl-4-hydroxycinnamate
• 4-coumaroyl-CoA into 4-coumaroylshikimate
• Quinate O-hydroxycinnamoyltransferase, the enzyme that transforms feruloyl-CoA into O-feruloylquinate
• sinapic acid) into 1-sinapoyl-D-glucose
• Coniferyl-alcohol glucosyltransferase, the enzyme that transforms coniferyl alcohol into coniferin

Deconjugation enzymes

• coniferol

Stilbenoids biosynthesis

• Pinosylvin synthase, an enzyme that transforms pinosylvin from cinnamoyl-CoA
• 4-coumaroyl-CoA to resveratrol
  .

An alternative bacterial

Coumarins biosynthesis

• Scopoletin glucosyltransferase, the enzyme that transforms scopoletin into scopolin

Chalcones biosynthesis

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

Hydroxycinnamic acids degradation

• 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.

References