Kinetic and molecular characterization of a maize UDP-Glycosyltransferase involved in flavonoid biosynthesis

JULIETA PETRICH; CASATI PAULA; ERICH GROTEWOLD; FALCONE FERREYRA, MARÍA LORENA

Simposio; V Encuentro & II Workshop de la Red Argentina de Tecnología Enzimática (Red TEz); 2023

Flavonoids are plant specialized metabolites widely distributed in plants. These compounds have different biological functions during growth and development and have protective roles against biotic and abiotic stressful conditions such as during pathogen infections, UV-B and high-fluence white light exposure, drought, cold and salinity. Moreover, flavonoids are well known for their beneficial effects on human health. One important aspect of flavonoid biosynthesis is its glycosylation, which increases its stability and solubility. As a result, plants typically accumulate flavonoids in the form of C- or O-, mono- or di- glycosylated derivatives. In this study, our aim was to functionally and kinetically characterize a novel UGT glycosyltransferase (ZmUGT2) which catalyzes the O- glycosylation of flavonoids in maize. Previous studies have shown that the expression of ZmUGT2 is induced by P1, a transcription factor involved in flavonoid biosynthesis. Phylogenetic analysis suggests that ZmUGT2 belongs to family 1 glycosyltransferases, which includes other UGTs involved in flavonoid O-glycosylation. To confirm the O-glucosyltransferase activity of ZmUGT2 with various flavonoids as acceptors, we used HPLC and MS analysis to analyze the reaction products. For all flavonoid types (flavanones, flavones and flavonols) tested as substrates, the enzyme showed a non-Michaelian response. We also determined the kinetic parameters of the enzyme with these acceptors, showing a higher catalytic efficiency when the substrate was kaempferol, a flavonol. Furthermore, we performed molecular exclusion analysis for further characterization of this enzyme. Overall, our study provides new insights into the flavonoid biosynthetic pathway in maize and sheds light on the function and kinetics of ZmUGT2, a novel O-glycosyltransferase that plays a role in the production of flavonoids in this important crop.