Fenylpropanoidpolulla

Fenylpropanoidpolulla, known in English as the phenylpropanoid pathway, is a central plant metabolic route that converts the amino acid phenylalanine into a diverse set of phenylpropanoid compounds. The pathway begins with phenylalanine being deaminated by phenylalanine ammonia-lyase (PAL) to form cinnamic acid; in some plants tyrosine ammonia-lyase (TAL) also contributes by supplying p-coumaric–type intermediates. Cinnamic acid is hydroxylated by cinnamate 4-hydroxylase (C4H) to p-coumaric acid, which is activated by 4-coumarate:CoA ligase (4CL) to p-coumaroyl-CoA. From this hub, branches diverge toward lignin biosynthesis, flavonoid and related polyphenols, and other hydroxycinnamic acid derivatives.

In lignin biosynthesis, further enzymes such as HCT, CCR, and CAD lead to monolignols (coniferyl, sinapyl, and p-coumaryl alcohols) that polymerize into lignin, reinforcing cell walls. In parallel, CHS and downstream enzymes channel flux toward flavonoids, anthocyanins, and proanthocyanidins, contributing to pigment and antioxidant functions. Additional branches produce coumarins, lignans, stilbenes, and various hydroxycinnamic acids. Regulation is coordinated by developmental signals and environmental cues (light, pathogens, wounding), with transcription factors from MYB, bHLH, and WD40 families modulating gene expression. The pathway supplies structural polymers, UV protection, defense-related compounds, and a broad spectrum of antioxidants, and serves as a versatile source of precursors for agricultural and biotechnological applications.