Nucleoside diphosphate sugars and saccharide synthesis

Leloir, Luis F.

doi:10.1042/bj0910001

Cited by 84 publications

(14 citation statements)

References 81 publications

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“…Because the activators are not incorporated into the polymer (27), their action seems to be similar to that of b-glucose-6-phosphate on glycogen synthetase. Leloir (4) suggested that the activator probably combines with some specific site on the enzyme surface causing a conformational change which affects the activity of the enzyme.…”

Section: Glycosidesmentioning

confidence: 99%

“…They are also converted by a series of enzymic reactions to sugar nucleotides, chiefly UDP-D-glucose (2), and to other sugar nucleotides, such as UDP-D-galactose, GDP-D-glucose, and ADP-D-glucose (3). The sugar moieties of these nucleotides are interconverted by various specific epimerases, and serve as donors for the formation of the numerous oligosaccharides and polysaccharides (4).…”

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confidence: 99%

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Biosynthesis of Oligosaccharides and Polysaccharides in Plants

Hassid

1969

Science

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Section: Glycosidesmentioning

confidence: 99%

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confidence: 99%

Biosynthesis of Oligosaccharides and Polysaccharides in Plants

Hassid

1969

Science

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“…GTs are found in all phylae. The nature of the acceptor molecules used is highly diverse, whereas the donor molecules typically are restricted to monosaccharides with either D-or L-configuration linked to a nucleotide (UDP/GDP/ CMP/(d)TDP; Leloir, 1964). Glycosylation reactions constitute an integral part of both primary and secondary metabolism.…”

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confidence: 99%

Determination of Catalytic Key Amino Acids and UDP Sugar Donor Specificity of the Cyanohydrin Glycosyltransferase UGT85B1 from Sorghum bicolor. Molecular Modeling Substantiated by Site-Specific Mutagenesis and Biochemical Analyses

Thorsøe¹,

Bak²,

Olsen³

et al. 2005

Plant Physiology

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Plants produce a plethora of structurally diverse natural products. The final step in their biosynthesis is often a glycosylation step catalyzed by a family 1 glycosyltransferase (GT). In biosynthesis of the cyanogenic glucoside dhurrin in Sorghum bicolor, the UDPglucosyltransferase UGT85B1 catalyzes the conversion of p-hydroxymandelonitrile into dhurrin. A structural model of UGT85B1 was built based on hydrophobic cluster analysis and the crystal structures of two bacterial GTs, GtfA and GtfB, which each showed approximately 15% overall amino acid sequence identity to UGT85B1. The model enabled predictions about amino acid residues important for catalysis and sugar donor specificity. p-Hydroxymandelonitrile and UDP-glucose (Glc) were predicted to be positioned within hydrogen-bonding distance to a glutamic acid residue in position 410 facilitating sugar transfer. The acceptor was packed within van der Waals distance to histidine H23. Serine S391 and arginine R201 form hydrogen bonds to the pyrophosphate part of UDP-Glc and hence stabilize binding of the sugar donor. Docking of UDP sugars predicted that UDP-Glc would serve as the sole donor sugar in UGT85B1. This was substantiated by biochemical analyses. The predictive power of the model was validated by site-directed mutagenesis of selected residues and using enzyme assays. The modeling approach has provided a tool to design GTs with new desired substrate specificities for use in biotechnological applications. The modeling identified a hypervariable loop (amino acid residues 156-188) that contained a hydrophobic patch. The involvement of this loop in mediating binding of UGT85B1 to cytochromes P450, CYP79A1, and CYP71E1 within a dhurrin metabolon is discussed.A glycosyltransferase (GT) is an enzyme that attaches a sugar molecule to a specific acceptor and thereby creates a glycosidic bond. GTs are found in all phylae. The nature of the acceptor molecules used is highly diverse, whereas the donor molecules typically are restricted to monosaccharides with either D-or L-configuration linked to a nucleotide (UDP/GDP/ CMP/(d)TDP; Leloir, 1964). Glycosylation reactions constitute an integral part of both primary and secondary metabolism. The final step in plant natural product synthesis is often a glycosylation reaction that serves to stabilize, solubilize, and provide a safe storage form of potentially toxic aglycones. In Sorghum bicolor, the GT UGT85B1 catalyzes glucosylation of Tyr-derived p-hydroxymandelonitrile to yield the cyanogenic glucoside dhurrin (Jones et al., 1999). In planta, neither p-hydroxymandelonitrile nor its degradation products are detectable, indicating that the glucosylation reaction is highly efficient and channeled (Møller and Conn, 1980). This observation has been substantiated by metabolome and transcriptome analyses of transgenic Arabidopsis (Arabidopsis thaliana) plants expressing the entire dhurrin pathway (Tattersall et al., 2001;Jørgensen et al., 2005;Kristensen et al., 2005), as well as by confocal laser-scanning microscopy studies ...

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“…Although adenosine diphosphate glucose (ADPG) is a more effective substrate for starch synthesis (Recondo and Leloir 1961), the concentration of UDPG in plant tissue is usually much higher than ADPG, thus compensating for the lower activity (Leloir 1964). In maturing pea seed, the concentration of hexose monophosphates (HMP) decreases (Rowan and Turner 1957) when the rate of synthesis of starch increases , coinciding with increased activity of amylose phosphorylase , and ADPG-and UDPG-pyrophosphorylase (Turner 1969a(Turner , 1969b.…”

Section: Introductionmentioning

confidence: 99%