Prenylation of Flavanones by an Aromatic Prenyltransferase from Fusarium globosum

Prenylation increases the structural diversity and biological activity of flavonoids. In this study, an aromatic prenyltransferase, FgPT1, was identified from <i>Fusarium globosum</i>. This enzyme was demonstrated to specifically catalyze the prenylation of flavanones, including naringenin, hesperitin, eriodictyol, liquiritigenin, rac-pinocembrin, and dihydrogenistein, and exhibited no activity toward other types of flavonoids, including chalcones, flavonols, isoflavonoids, and flavonols. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and nuclear magnetic resonance (NMR) analysis indicated that the majority of prenylated products were 6-<i>C</i> prenyl flavanones, with the exception of liquiritigenin, which was additionally transformed to 4'-<i>O</i> prenyl liquiritigenin. Enzyme kinetic analysis suggested that FgPT1 exhibited the highest catalytic efficiency towards naringenin, with a <i>k_cat</i>/<i>K_M</i> value determined as 61.92 s^-1 M^-1, and the lowest catalytic efficiency towards liquiritigenin, with a <i>k_cat</i>/<i>K_M</i> of 1.18 s^-1 M^-1. Biochemical characterization suggested that FgPT1 functioned as a metal-dependent enzyme with optimal activity in the presence of Ba²⁺ at pH 7.5 and 30 °C. Site-directed mutagenesis resulted in a series of mutants, including A325V with impaired prenylation activity and V116I, V181I, and V194I with enhanced activity. V194I displayed the highest enzymatic activity with a nine-fold increase compared to wild-type FgPT1.