UDP-Sugar Producing Pyrophosphorylases: Distinct and Essential Enzymes With Overlapping Substrate Specificities, Providing de novo Precursors for Glycosylation Reactions

Abstract

Nucleotide sugars are the key precursors for all glycosylation reactions and are required both for oligo- and polysaccharides synthesis and protein and lipid glycosylation. Among all nucleotide sugars, UDP-sugars are the most important precursors for biomass production in nature (e.g., synthesis of cellulose, hemicellulose, and pectins for cell wall production). Several recent studies have already suggested a potential role for UDP-Glc in plant growth and development, and UDP-Glc has also been suggested as a signaling molecule, in addition to its precursor function. In this review, we will cover primary mechanisms of formation of UDP-sugars, by focusing on UDP-sugar metabolizing pyrophosphorylases. The pyrophosphorylases can be divided into three families: UDP-Glc pyrophosphorylase (UGPase), UDP-sugar pyrophosphorylase (USPase), and UDP-N-acetyl glucosamine pyrophosphorylase (UAGPase), which can be distinguished both by their amino acid sequences and by differences in substrate specificity. Substrate specificities of these enzymes are discussed, along with structure-function relationships, based on their crystal structures and homology modeling. Earlier studies with transgenic plants have revealed that each of the pyrophosphorylases is essential for plant survival, and their loss or a decrease in activity results in reproductive impairment. This constitutes a problem when studying exact in vivo roles of the enzymes using classical reverse genetics approaches. Thus, strategies involving the use of specific inhibitors (reverse chemical genetics) are also discussed. Further characterization of the properties/roles of pyrophosphorylases should address fundamental questions dealing with mechanisms and control of carbohydrate synthesis and may allow to identify targets for manipulation of biomass production in plants.

Plant Cell Walls Tackling Climate Change: Biotechnological Strategies to Improve Crop Adaptations and Photosynthesis in Response to Global Warming

“…Nucleotide sugars, such as uridine diphosphate glucose (UDP-Glc), constitute the precursors for synthesis of CW polysaccharides [35]. Metabolic pathways of sucrose catabolism and provision of UDP-Glc for CW have been well reported [36][37][38].…”

“…CW synthesis requires sucrose as the source of C and energy ( Figure 2). Several mechanisms for nucleotide-sugar formation contribute to cell wall synthesis [35]. As schematized in Figure 2, sucrose synthase (SuSy) and invertases play a tightly coordinated and fundamental role in CW formation because they are involved in the synthesis of precursor sugars required for cell wall components.…”

“…CW polysaccharides are composed of a mixture of different sugars (not only glucose) and, prior to be incorporated into the polysaccharide matrix, these need to be activated to nucleotide sugars by specific post-translational modifications (such as redox regulation, phosphorylation, oligomerization, etc.) which reflect responses to climate change [35,39,40]. Therefore, climate change induced alterations of NDP-sugar supply to polysaccharide synthases could affect CW synthesis and structure.…”

Biochemical characterization of recombinant UDP-sugar pyrophosphorylase and galactinol synthase fromBrachypodium distachyon

“…Plant USPPases show activity with different sugar 1-phosphates (Decker and Kleczkowski, 2019). To test which metabolites could be used by BdiUSPPase, we measured activity with a fixed concentration (2 mM) of Gal1P, Glc1P, GlcA1P, glucosamine 1-phosphate (GlcN1P), N-acetyl-glucosamine 1-phosphate (GlcNAc1P), and mannose 1-phosphate (Man1P).…”

“…1) is in good agreement with the theoretical value and with data reported for USPPases from dicot species (Kotake et al, 2004;Dai, 2006;Litterer et al, 2006b,a). Recombinant BdiUSPPase is active as a monomer and, unlike parasite and plant UDP-Glc pyrophosphorylases, there is no evidence for oligomerization (Damerow et al, 2010;Decker and Kleczkowski, 2019). The reaction catalyzed by USPPase is reversible (Kleczkowski et al, 2010(Kleczkowski et al, , 2011 and Mg 2+ -dependent (Litterer et al, 2006a;Mu et al, 2009;Yang et al, 2010), following an ordered bi-bi mechanism (Kleczkowski et al, 2011).…”