The enzymic conversion of hydroxycinnamic acids to p-coumarylquinic and chlorogenic acids in tomato fruits |
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Authors: | Michael J.C. Rhodes Leonard S.C. Wooltorton |
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Affiliation: | A.R.C. Food Research Institute, Colney Lane, Norwich NR4 7UA, England |
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Abstract: | Two enzymes thought to be involved in the biosynthesis of chlorogenic acid have been separated and purified by ion exchange chromatography and their properties studied. These two enzymes, p-coumarate CoA ligase and hydroxycinnamyl CoA: quinate hydroxycinnamyl transferase, acting together catalyse the conversion of p-coumaric acid to 5′-p-coumarylquinic acid and of caffeic acid to chlorogenic acid. The ligase has a higher affinity for p-coumaric than for caffeic acid and will in addition activate a number of other cinnamic acids such as ferulic, isoferulic and m-coumaric acids but not cinnamic acid. The transferase shows higher activity and affinity with p-coumaryl CoA than caffeyl CoA. It also acts with ferulyl CoA but only very slowly. The enzyme shows high specificity for quinic acid; shikimic acid is esterified at only 2% of the rate with quinic acid and glucose is not a substrate. The transferase activity is reversible and both chlorogenic acid and 5′-p-coumarylquinic acids are cleaved in the presence of CoA to form quinic acid and the corresponding hydroxycinnamyl CoA thioester. |
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Keywords: | Solanaceae tomato fruit chlorogenic acid biosynthesis hydroxycinnamate CoA ligase hydroxycinnamyl CoA: quinate: hydroxycinnamyl transferase. |
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