ChalconeSynthase

Chalcone synthase (CHS) is a plant enzyme that catalyzes the first committed step in the biosynthesis of flavonoids. It belongs to the type III polyketide synthase family and typically forms homodimers of about 42–45 kDa, with subunits of roughly 389 amino acids. CHS is widely studied in flowering plants, where multiple CHS genes may be present.

CHS catalyzes the condensation of one molecule of p-coumaroyl-CoA with three molecules of malonyl-CoA to yield naringenin chalcone, which is subsequently converted to the flavanone naringenin by chalcone isomerase. The overall reaction releases four CoA and three CO2 molecules. The reaction proceeds through a covalent intermediate formed on a catalytic cysteine residue, with subsequent decarboxylative condensations and cyclization that produce the chalcone core.

Genetic and regulatory aspects: CHS genes are often developmentally regulated and respond to light, UV exposure, and plant hormones. Expression patterns typically correspond to tissues rich in flavonoids, such as petals, seed coats, and fruit epidermis, contributing to pigmentation and UV protection.

Significance and applications: CHS is a key control point in flavonoid biosynthesis, influencing flower color, pollen viability, and defense responses. It has been exploited in metabolic engineering to produce flavonoids and related polyketides in plants and heterologous systems.