Glycosyltransferases of Small Molecules: Their Roles in Plant Biology

Abstract

Glycosyltransferases are enzymes that transfer sugars from nucleotide sugars to a wide range of small molecule acceptors, from hormones and secondary metabolites to biotic and abiotic chemicals. This alters the hydrophilicity of the acceptors, their stability and chemical properties, their subcellular localization and often their bioactivity. Glycosyltransferases form a large multigene family in the plant kingdom and can be identified by a signature motif in their primary sequence. Considerable progress has been made in understanding the biochemistry of glycosyltransferases and the role of these enzymes in the plant. This article outlines our current knowledge of these enzymes, drawing on information gained from recent in vitro and in planta studies. Key concepts: There is a class of glycosyltransferases (GTs) that transfers sugars to small molecule acceptors. In plants, these acceptors can be natural products such as hormones and secondary metabolites, as well as nonnatural products, such as herbicides and pesticides. Glycosylation changes the properties of the acceptors, increasing water solubility and leading to transport of glycosides from the cytosol. Glycosylation can also affect activity of the acceptors, both in the plant, such as inactivation of hormones and in industrial applications, such as bioactivity and bioavailability.

Glycosidically Bound Volatile Aroma Compounds in Grapes and Wine: A Review

“…For example, linalool has a predicted log octanol water coefficient of 3.38, but when glycosylated it has a predicted log K ow of 2.33 (estimates using KOWWIN in EPISuite, www.epa.gov/opptintr/exposure/ pubs/episuite.htm). The addition of a sugar moiety greatly increases the solubility of the compounds, preventing diffusion across cellular membranes, and thus provides a convenient storage form (Bowles and Lim 2010).…”

Identification of a Bifunctional Maize C- and O-Glucosyltransferase

“…The glycosyltransferases that use uridine diphosphate (UDP) sugar molecules as donors are referred to as UDP-dependent glycosyltransferases (UGTs), 4 and they are members of glycosyltransferase family 1 (1,2). This family contains most plant UGTs, which utilize different small molecules derived from specialized metabolisms as acceptors, such as terpenoids, flavonoids, saponins, plant hormones, and xenobiotics (2).…”

“…Thus, plant UGTs are involved in different cellular processes that include specialized metabolism, modification of plant hormones, detoxification of xenobiotics, and plant-pathogen interactions. The glycosylation of specialized metabolites, such as flavonoids, affect their properties, enhancing their stability and solubility, and are believed to be important for the compartmentalization, storage, and biological activity of many specialized metabolites (3)(4)(5)(6)(7)(8). Flavonoids are classified in six major subgroups, chalcones, flavones, flavonols, flavandiols, anthocyanins, and proanthocyanidins or condensed tannins, and a few species also produce aurones, isoflavonoids, 3-deoxyanthocyanins, and phlobaphenes (9).…”

Cloning and Site Directed Mutagenesis of UGT76E1 Leads to Changed Substrate Activity in Arabidopsis thalian

“…Glycosyltransferases (GTs) participate in glycosylation reaction and change the hydrophilicity of living molecules. This change helps to detoxify the natural products along with their stabilization and also regulates the cellular signaling (Sakakibara, 2009;Bowles and Lim, 2010;Barvkar et al, 2012).…”

“…Glycosylation may occur at single or multiple groups (-OH, -COOH, -NH2, -SH and C-C) of acceptor molecules . The acceptor molecules for GTs in plants are their own metabolites and xenobiotics, mevalonate derivatives, polyketides, amino acid derivatives and certain other synthetic chemicals (Bowles and Lim, 2010). Transfer of sugar molecule to any acceptor molecule changes its biochemical properties as well as its bioactivity (Vogt and Jones, 2000;.…”