The role of carbohydrates in biologically active natural products

Weymouth‐Wilson, Alexander C.

doi:10.1039/np9971400099

Cited by 536 publications

(326 citation statements)

References 99 publications

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“…ribose-5-phosphate | natural product | biosynthesis | Streptomyces C arbohydrates are abundant constituents of natural products, which are often essential for the biological activity and solubility of the compounds (1). Structure/function studies have identified that many medically important compounds in clinical use, such as the antibiotic erythromycin (2) and the anthracycline anticancer agents doxorubicin (3) and aclacinomycin (4), owe their activity to the deoxysugar moieties.…”

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confidence: 99%

Biosynthetic pathway toward carbohydrate-like moieties of alnumycins contains unusual steps for C-C bond formation and cleavage

Oja

Klika

Appassamy

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Carbohydrate moieties are important components of natural products, which are often imperative for the solubility and biological activity of the compounds. The aromatic polyketide alnumycin A contains an extraordinary sugar-like 4′-hydroxy-5′-hydroxymethyl-2′,7′-dioxane moiety attached via a carbon-carbon bond to the aglycone. Here we have extensively investigated the biosynthesis of the dioxane unit through 13 C labeling studies, gene inactivation experiments and enzymatic synthesis. We show that AlnA and AlnB, members of the pseudouridine glycosidase and haloacid dehalogenase enzyme families, respectively, catalyze C-ribosylation conceivably through Michael-type addition of D-ribose-5-phosphate and dephosphorylation. The ribose moiety may be attached both in furanose (alnumycin C) and pyranose (alnumycin D) forms. The C 1 0 -C 2 0 bond of alnumycin C is subsequently cleaved and the ribose unit is rearranged into an unprecedented dioxolane (cisbicyclo[3.3.0]-2′,4′,6′-trioxaoctan-3′β-ol) structure present in alnumycin B. The reaction is catalyzed by Aln6, which belongs to a previously uncharacterized enzyme family. The conversion was accompanied with consumption of O 2 and formation of H 2 O 2 , which allowed us to propose that the reaction may proceed via hydroxylation of C1′ followed by retro-aldol cleavage and acetal formation. Interestingly, no cofactors could be detected and the reaction was also conducted in the presence of metal chelating agents. The last step is the conversion of alnumycin B into the final end-product alnumycin A catalyzed by Aln4, an NADPH-dependent aldo-keto reductase. This characterization of the dioxane biosynthetic pathway sets the basis for the utilization of C-C bound ribose, dioxolane and dioxane moieties in the generation of improved biologically active compounds.ribose-5-phosphate | natural product | biosynthesis | Streptomyces

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confidence: 99%

Biosynthetic pathway toward carbohydrate-like moieties of alnumycins contains unusual steps for C-C bond formation and cleavage

Oja

Klika

Appassamy

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…This paradigm is found throughout the anticancer and antiinfective arenas with representative clinical examples (Fig. 1a), including enediynes (calicheamicin, 1), polyketides (doxorubicin, 2; erythromycin, 3), indolocarbazoles (staurosporine, 4), nonribosomal peptides (vancomycin, 5), polyenes (nystatin, 6), coumarins (novobiocin, 7), and cardiac glycosides (digitoxin, 8) (1)(2)(3)(4)(5)(6)(7). Given the importance of the sugars attached to these and other biologically significant metabolites, extensive effort has been directed in recent years toward altering sugars as a means to enhance or alter natural product-based therapeutics by both in vivo and in vitro approaches (ref.…”

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confidence: 99%

Creation of the first anomeric D/L-sugar kinase by means of directed evolution

Hoffmeister

Yang²,

Liu³

et al. 2003

Proceedings of the National Academy of Sciences

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Chemoenzymatic routes toward complex glycoconjugates often depend on the availability of sugar-1-phosphates. Yet the chemical synthesis of these vital components is often tedious, whereas natural enzymes capable of anomeric phosphorylation are known to be specific for one or only a few monosaccharides. Herein we describe the application of directed evolution and a high-throughput multisugar colorimetric screen to enhance the catalytic capabilities of the Escherichia coli galactokinase GalK. From this approach, one particular GalK mutant carrying a single amino acid exchange (Y371H) displayed a surprisingly substantial degree of kinase activity toward sugars as diverse as D-galacturonic acid, D-talose, L-altrose, and L-glucose, all of which failed as wild-type GalK substrates. Furthermore, this mutant provides enhanced turnover of the small pool of sugars converted by the wild-type enzyme. Comparison of this mutation to the recently solved structure of Lactococcus lactis GalK begins to provide a blueprint for further engineering of this vital class of enzyme. In addition, the rapid access to such promiscuous sugar C-1 kinases will significantly enhance accessibility to natural and unnatural sugar-1-phosphates and thereby impact both in vitro and in vivo glycosylation methodologies, such as natural product glycorandomization.galactokinase ͉ glycorandomization ͉ in vitro evolution ͉ enzyme M any clinically important medicines are derived from glycosylated natural products, the D-or L-sugar substituents of which often dictate their overall biological activity. This paradigm is found throughout the anticancer and antiinfective arenas with representative clinical examples (Fig. 1a), including enediynes (calicheamicin, 1), polyketides (doxorubicin, 2; erythromycin, 3), indolocarbazoles (staurosporine, 4), nonribosomal peptides (vancomycin, 5), polyenes (nystatin, 6), coumarins (novobiocin, 7), and cardiac glycosides (digitoxin, 8) (1-7). Given the importance of the sugars attached to these and other biologically significant metabolites, extensive effort has been directed in recent years toward altering sugars as a means to enhance or alter natural product-based therapeutics by both in vivo and in vitro approaches (ref. 8 and references therein). Among these, in vitro glycorandomization (IVG) makes use of the inherent or engineered substrate promiscuity of nucleotidylyltransferases and glycosyltransferases to activate and attach chemically synthesized sugar precursors to various natural product scaffolds (6,7,(9)(10)(11)(12)(13)(14)(15), the advantage of which is the ability to efficiently incorporate highly functionalized ''unnatural'' sugar substitutions into the corresponding natural product scaffold (Fig. 1b). In a recent demonstration of IVG, Ͼ50 analogs of 5 were generated, some of which displayed enhanced and distinct antibacterial profiles from the parent natural product (13).As starting materials, sugar phosphates play a key role in the entire IVG process. Thus, the ability to rapidly construct sugar phosphate ...

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“…Carbohydrates are vital in nature, not only for energy metabolism, but also as structural scaffolds, recognition motifs, solubility aids, and functional modulators (1,2). Yet, despite the vast structural and functional diversity of natural glycoconjugates, they are constructed via a common biosynthetic theme.…”

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confidence: 99%

Enhancing the Latent Nucleotide Triphosphate Flexibility of the Glucose-1-phosphate Thymidylyltransferase RmlA

Moretti

Thorson

2007

Journal of Biological Chemistry

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Nucleotidyltransferases are central to nearly all glycosylationdependent processes and have been used extensively for the chemoenzymatic synthesis of sugar nucleotides. The determination of the NTP specificity of the model thymidylyltransferase RmlA revealed RmlA to utilize all eight naturally occurring NTPs with varying levels of catalytic efficiency, even in the presence of nonnative sugar-1-phosphates. Guided by structural models, active site engineering of RmlA led to alterations of the inherent pyrimidine/purine bias by up to three orders of magnitude. This study sets the stage for engineering single universal nucleotidyltransferases and also provides new catalysts for the synthesis of novel nucleotide diphosphosugars.Carbohydrates are vital in nature, not only for energy metabolism, but also as structural scaffolds, recognition motifs, solubility aids, and functional modulators (1, 2). Yet, despite the vast structural and functional diversity of natural glycoconjugates, they are constructed via a common biosynthetic theme. Specifically, sugars are attached to most proteins, lipids, carbohydrates, and small molecules by glycosyltransferases, which with few exceptions use sugar nucleotides as the monosaccharide donors (3-7). These sugar nucleotides are constructed from sugar-1-phosphates and NTPs by sugar-1-phosphate nucleotidyltransferases, also referred to as sugar nucleotide pyrophosphorylases (EC 2.7.7.-), providing the precursors (usually ADP-, CDP-, GDP-, UDP-and dTDP-glucoses, as well as GDP-mannose, GDP-fucose, and UDP-N-acetylglucosamine) central to nearly all glycosylation-dependent processes (4, 6).Nucleotidyltransferases are prevalent in nature (there are currently ϳ14,000 known and putative nucleotidyltransferase sequences in GenBank TM (8)), are often allosterically controlled, and generally proceed via an ordered bi-bi mechanism. For example, the forward reaction catalyzed by Salmonella glucose-1-phosphate thymidylyltransferase (RmlA) (9) proceeds via a direct S N 2 attack upon the NTP ␣-phosphate by an ␣-Dsugar anomeric phosphate to provide the desired sugar nucleotide and pyrophosphate (Fig. 1). Nucleotidyltransferases from both prokaryotes and eukaryotes have reported flexibility toward variant sugar phosphates in vitro (10 -18), and the uniquely broad sugar-1-phosphate tolerance of RmlA has been exploited for the synthesis of diverse UDP-and dTDP-based sugar nucleotide libraries and enhanced via structure-based engineering (9 -13). To date, more than 30 different sugar-1-phosphates have been reported as substrates for RmlA variants (9 -13, 19).The corresponding pyrimidine-based sugar nucleotide libraries have served as the foundation for a process known as natural product glycorandomization (Fig. 1B), an enzymatic strategy to exchange natural product sugars with diverse sugar arrays (18). To date, this strategy has been applied toward the diversification of glycopeptide, coumarin, and macrolide antibiotics (19 -24), the anthelmintic avermectin (25) and enediyne anticancer agents (22). Yet,...

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The role of carbohydrates in biologically active natural products

Cited by 536 publications

References 99 publications

Biosynthetic pathway toward carbohydrate-like moieties of alnumycins contains unusual steps for C-C bond formation and cleavage

Biosynthetic pathway toward carbohydrate-like moieties of alnumycins contains unusual steps for C-C bond formation and cleavage

Creation of the first anomeric D/L-sugar kinase by means of directed evolution

Enhancing the Latent Nucleotide Triphosphate Flexibility of the Glucose-1-phosphate Thymidylyltransferase RmlA

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