Molecular cloning and enzymatic characteristics of chalcone isomerase from Rheum palmatum

Abstract

Rheum palmatum has been widely developed in traditional Chinese medicine. One of the major active compounds in R.palmatum is flavonoids. Until now, few genes involved in flavonoid biosynthesis have been isolated from this medicinal plant. In thisstudy, a new chalcone isomerase gene (RpCHI) was cloned from an RNA-seq library of R. palmatum. The 714bp RpCHI cDNA wascloned and sequenced. The RpCHI recombinant protein was successfully overexpressed in a prokaryotic expression system and purifiedto homogeneity by a nickel-nitrilotriacetic acid (Ni-NTA) prepacked column, and the enzymatic activity was investigated. The resultshave clarified that RpCHI was assembled into the type I CHI group based on phylogenetic analysis. Activity examination revealed thatRpCHI exhibits high substrate affinity for naringenin chalcone, and it can also use isoliquiritigenin in relatively low activity. OptimumpH and temperature for enzymatic reaction was determined to be 7.0 and 40 °C, respectively. RpCHI was successfully cloned in theexperiment, and the enzymatic activity revealed RpCHI uses various substrates to produce antioxidant flavonoids.