Artichoke (Cynara cardunculus var. scolymus L.) is used not only as an edible vegetable, but also for its beneficial medical properties. Various potential pharmacodynamic effects have been observed in vitro for mono- and dicaffeoylquinic acids (e.g. chlorogenic acid, cynarin), caffeic acid and flavonoids (e.g. luteolin-7-O-glucoside) which are the main phenolic constituents of artichoke extracts. The polyphenolic fractions are abundant in artichoke plant organs and bioavailable to humans by oral consumption. The aim of our study is to acquire new knowledge in the metabolism of caffeoylquinic acids in artichoke, by isolating and studying the genes involved in the synthesis of these compounds. In particular, we are focusing on the genes coding for HQT (hydroxycinnamoyl-CoA quinate:hydroxycinnamoyl transferase), a BAHD acyl transferase synthesing chlorogenic acid in other plants. We report on the isolation and characterization of two full-length hqt cDNAs from artichoke leaves. These sequences showed a high level of similarity to hqt genes from other plants. A phylogenetic analysis of the putative HQT protein sequences from artichoke together with other acyltransferase sequences, showed that the two artichoke HQTs cluster together and belong to a bigger group of HQT-encoding genes from tobacco, tomato, potato, and coffee. On the other hand, the sequences of another acyl transferase, HCT, form a separate cluster. The two artichoke hqt cDNAs were cloned in an S-TAG vector and expressed in E. coli, to confirm HQT activity. To better characterize their biochemical properties, kinetic analyses were performed using the recombinant HQT proteins with different substrates. Moreover, gene expression was evaluated by real time PCR in leaves and flower heads of some genotypes belonging to the IGV artichoke collection.
The synthesis of chlorogenic acid in artichoke: comparison of two newly isolated hqt genes
Pignone D;Sonnante G
2008
Abstract
Artichoke (Cynara cardunculus var. scolymus L.) is used not only as an edible vegetable, but also for its beneficial medical properties. Various potential pharmacodynamic effects have been observed in vitro for mono- and dicaffeoylquinic acids (e.g. chlorogenic acid, cynarin), caffeic acid and flavonoids (e.g. luteolin-7-O-glucoside) which are the main phenolic constituents of artichoke extracts. The polyphenolic fractions are abundant in artichoke plant organs and bioavailable to humans by oral consumption. The aim of our study is to acquire new knowledge in the metabolism of caffeoylquinic acids in artichoke, by isolating and studying the genes involved in the synthesis of these compounds. In particular, we are focusing on the genes coding for HQT (hydroxycinnamoyl-CoA quinate:hydroxycinnamoyl transferase), a BAHD acyl transferase synthesing chlorogenic acid in other plants. We report on the isolation and characterization of two full-length hqt cDNAs from artichoke leaves. These sequences showed a high level of similarity to hqt genes from other plants. A phylogenetic analysis of the putative HQT protein sequences from artichoke together with other acyltransferase sequences, showed that the two artichoke HQTs cluster together and belong to a bigger group of HQT-encoding genes from tobacco, tomato, potato, and coffee. On the other hand, the sequences of another acyl transferase, HCT, form a separate cluster. The two artichoke hqt cDNAs were cloned in an S-TAG vector and expressed in E. coli, to confirm HQT activity. To better characterize their biochemical properties, kinetic analyses were performed using the recombinant HQT proteins with different substrates. Moreover, gene expression was evaluated by real time PCR in leaves and flower heads of some genotypes belonging to the IGV artichoke collection.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
