stilbenesyntase

Stilbene synthase, often abbreviated STS, is a plant type III polyketide synthase involved in the biosynthesis of stilbenes, a class of phenolic compounds that includes resveratrol. The enzyme catalyzes the condensation of one molecule of p-coumaroyl-CoA with three molecules of malonyl-CoA, followed by cyclization and aromatization to produce resveratrol, although it can generate related stilbenes depending on substrate availability and enzyme variant.

STS belongs to the chalcone synthase-like subgroup of type III polyketide synthases. It typically functions as a cytosolic enzyme and operates as a homodimer. The mechanism uses a conserved catalytic triad (Cys-His-Asn) and proceeds via sequential decarboxylative condensations of CoA thioesters, yielding the characteristic stilbene skeleton. Structural similarities with chalcone synthase account for overlapping substrate affinities, but STS prefers stilbene-forming cyclization rather than the alternative chalcone route.

Distribution and regulation: Stilbene synthase genes are widely distributed in flowering plants, with notable members identified in grapevine (Vitis vinifera), peanut (Arachis hypogaea), and other species. STS genes are often inducible by biotic and abiotic stresses, including pathogen attack, wounding, UV exposure, and elicitors such as salicylic acid or methyl jasmonate. This inducible expression supports the role of stilbenes as phytoalexins and antioxidants in plant defense.

Significance: Stilbenes, particularly resveratrol, have attracted interest for their proposed health benefits and potential biotechnological applications. STS enzymes are studied for metabolic engineering to enhance stilbene production in plants and microbial systems.