Substrate specificity change of a flavonoid prenyltransferase AhPT1 induced by metal ion

Abstract

Prenylated flavonoids are good drug candidates due to multiple biological activities and health benefits. Prenyltransferase is an important enzyme involved in the biosynthesis of prenylated flavonoids. In this work, a flavonoid prenyltransferase (AhPT1) from Artocarpus heterophyllus showed an unexpectedly metal ion-induced specificity to flavonoid substrates. AhPT1 could catalyse 6-C-prenylation of genistein when Mg2+ serving as cofactor. Its catalytic activity to 6-hydroxyflavone was undetectable. However, when Mn2+ was used instead of Mg2+, 5-C-prenylated 6-hydroxyflavone was generated with a high conversion rate. Mn2+ altered the regiospecificity of AhPT1 and turned it into a 5-C-prenyltransferase. 2′-Hydroxyl could improve the conversion rate of 6-hydroxyflavone, whereas 3′- or 4′-hydroxyl impaired the catalysis efficiency of AhPT1. NQIFDADID174 and DLTDVEGD305 were active motifs involved in substrate binding and catalysis. Asn166, Asp170, Asp174, Asp298, Asp301 and Asp305 in the active center were critical to the prenylation reaction.