Advances in flavonoid glycosyltransferase research: integrating recent findings with long-term citrus studies

Abstract

Flavonoid glycosides are required for a number of crucial roles in planta and have the potential for development in a variety of agricultural, medicinal, and biotechnological applications. A number of recent advancements have been made in characterizing glycosyltransferases, the enzymes that are responsible for the synthesis of these important molecules. In this review, glycosyltransferases are considered with regard to biochemical properties, expression patterns, levels of enzyme activity during development, and structure/function relationships. This is presented with historical context to highlight critical findings, particularly with regard to the innovative work that has come from research on citrus species. The plant glycosyltransferase crystal structures that have been solved over the past decade, either alone or in complex with sugar donor and/or acceptor molecules, are discussed. The application of results from these structures to inform current structure/function work as well as implications and goals for future crystallography and tertiary modeling studies are considered. A thorough understanding of the properties of glycosyltransferases will be a critical step in any future biotechnological application of these enzymes in areas such as crop improvement and custom design of enzymes to produce desired compounds for nutritional and/or medicinal usage.

The Effect of Recombinant Tags on Citrus paradisi Flavonol-Specific 3-O Glucosyltransferase Activity

“…Initial characterizations of pH optima for Cp3GT, obtained through expression in E. coli, indicated an optimal pH of 7-7.5, which is indicative of a normal physiological pH. This agrees with other flavonoid glucosyltransferase (GT) pH optima of 6.5-8 [25][26][27]. More recent characterizations of Cp3GT expressed using P. pastoris, however, showed a higher optimal pH of 8.5-9.…”

“…To make a comparison regarding pH optima between tagged and untagged enzyme, Cp3GT activity was measured over a pH range of 5.5-9.5 using various buffers that overlapped in pH. Among plant GT's, pH optima tend to align with physiological pH (7-7.5) but can vary as high as 9 and as low as 5.5 when expressed in recombinant systems [26,[28][29][30]. A shift away from physiological pH could suggest that conditions surrounding the expression and preparation of the enzyme are influencing stability and activity, especially for enzymes such as plant GT's that have structural similarity.…”

Association mapping for total polyphenol content, total flavonoid content and antioxidant activity in barley

“…UDP-glycosyltransferases (UGTs) are often characterized by a conserved plant secondary product glycosyltransferase (PSPG) box of 44 amino acids binding UDP-conjugates as their activated sugar donor substrates. In plants, UGTs are involved in the transferring of glycosyl moieties into a wide range of acceptors including flavonoids in the process of glycosylation [ 12 ]. A few UGT protein coding genes are associated with biosynthesis of flavonoid glycosides in Arabidopsis thaliana and soybean ( Glycine max ) [ 13 , 14 ].…”

Metabolic Variations of Flavonoids in Leaves of T. media and T. mairei Obtained by UPLC-ESI-MS/MS

“…Chrysoeriol not only possesses many biological effects similar to luteolin, such as antioxidant and anti-inflammatory effects, but also exhibits its own effects, such as osteoporosis [36]. The glycosides conferred a huge diversity to the structure of tricin and chrysoeriol, which may further enrich their biological functions and pharmacological effects [37].…”