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.

Keywords: glycosyltransferases; homeostasis; hormones; secondary metabolites

Figure 1.

(a)–(i) The chemical structures of plant metabolites are shown in these panels, with their glycosylation sites highlighted. (j) The metabolic relatedness of the compounds is illustrated. Reproduced from Bowles et al.. With permission from Annual Reviews, Inc.

Figure 2.

Phylogenetic analysis of the Arabidopsis UGT superfamily shows 14 distinct groups. The tree shown was derived by neighbour‐joining distance analysis. Bootstrap values over 50% are indicated above the nodes, with the number on the left for the neighbour‐joining and right for parsimony. Hypothetical intron gains and losses are indicated by diamonds, followed by intron number. Postulated intron gains are indicated by filled diamonds, intron losses by unfilled diamonds and the questionable intron loss by striped diamonds. Reproduced from Bowles et al.. With permission from Annual Reviews, Inc.

Figure 3.

Glycosylation of esculetin by ArabidopsisGTs in phylogenetic group E. The regioselective glycosylation of esculetin falls into two subsets within group E, with the exception of UGT72B1 and UGT72B3, which suggests that a regioselectivity switching event has occurred during the gene's evolution. GTs not analysed are labelled in black.

Figure 4.

Flavonol glycosylation in Arabidopsis.

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Further Reading

Dewick PM (1997) Medicinal Natural Products. Chichester, UK: Wiley.

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Bowles, Dianna, and Lim, Eng‐Kiat(Apr 2010) Glycosyltransferases of Small Molecules: Their Roles in Plant Biology. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0021537]