Biotransformation of cinnamic acid

The biotransformation of cinnamic acid is a fundamental metabolic process primarily observed in plants, fungi, and bacteria, as well as in the detoxification systems of animals. In the plant kingdom, it represents the critical entry point into the phenylpropanoid pathway, where cinnamic acid is hydroxylated to p-coumaric acid by the enzyme cinnamate 4-hydroxylase (C4H), a member of the cytochrome P450 family. This transformation is vital for the production of secondary metabolites such as lignin, flavonoids, and coumarins, which are essential for structural support and defense. In animals, exogenous cinnamic acid undergoes mitochondrial beta-oxidation to form benzoic acid, which is subsequently conjugated with glycine to produce hippuric acid for urinary excretion. While the pathway itself is not a traditional therapeutic target for human medicine, specific enzymes within it, such as phenylalanine ammonia-lyase (PAL) and C4H, are significant targets in agricultural biotechnology for modifying plant traits and in microbial engineering for the industrial synthesis of aromatic compounds. Furthermore, derivatives generated through this pathway, such as caffeic and ferulic acids, are extensively researched for their antioxidant, anti-inflammatory, and anticancer properties.

Other names

Cinnamate metabolismPhenylpropanoid pathway (initial steps)Cinnamic acid degradation pathwayConversion of cinnamic acid to benzoic acid

Modulation of the pathway occurs through the inhibition of specific enzymes such as Phenylalanine ammonia-lyase (PAL) or Cinnamate 4-hydroxylase (C4H), which regulates the flux of metabolites into the phenylpropanoid and lignin biosynthetic routes.