Substrate specificity of chalcone synthase from Petroselinum hortense. Formation of phloroglucinol derivatives from aliphatic substrates.
The substrate specificity of chalcone synthase, the key enzyme of flavonoid biosynthesis, was investigated. A purified enzyme preparation from cell suspension cultures of parsley (Petroselinum hortense) catalyzed chain elongations with acetate units from malonyl-CoA, using various aromatic and aliphatic CoA esters as starter molecules. Malonyl-CoA could not be replaced by malonyl acyl carrier protein in the standard chalcone synthase assay. Butyryl-CoA, hexanoyl-CoA, and benzoyl-CoA served as substrates for the condensation reaction with similar efficiency as 4-coumaroyl-CoA, the natural substrate of the enzyme. Acetyl-CoA and octanoyl-CoA were relatively poor substrates. Among the products formed with the two most efficient aliphatic substrates tested, butyryl-CoA and hexanoyl-CoA, were the respective chalcone analogues, phlorobutyrophenone and phlorocaprophenone. The possibility is discussed that chalcone synthase and the corresponding enzyme of fatty acid synthesis in higher plants, beta-ketoacyl-acyl carrier protein synthase, have a common evolutionary origin.
D000105:Acetyl Coenzyme A; D000217:Acyltransferases / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D010696:Phloroglucinol / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D002250:Carbon Radioisotopes; D000105:Acetyl Coenzyme A; D010696:Phloroglucinol; D000217:Acyltransferases; C020141:flavanone synthetase