The glycome describes the complete repertoire of glycoconjugates composed of carbohydrate chains, or glycans, that are covalently linked to lipid or protein molecules. Glycoconjugates are formed through a process called glycosylation and can differ in their glycan sequences, the connections between them and their length. Glycoconjugate synthesis is a dynamic process that depends on the local milieu of enzymes, sugar precursors and organelle structures as well as the cell types involved and cellular signals. Studies of rare genetic disorders that affect glycosylation first highlighted the biological importance of the glycome, and technological advances have improved our understanding of its heterogeneity and complexity. Researchers can now routinely assess how the secreted and cell-surface glycomes reflect overall cellular status in health and disease. In fact, changes in glycosylation can modulate inflammatory responses, enable viral immune escape, promote cancer cell metastasis or regulate apoptosis; the composition of the glycome also affects kidney function in health and disease. New insights into the structure and function of the glycome can now be applied to therapy development and could improve our ability to fine-tune immunological responses and inflammation, optimize the performance of therapeutic antibodies and boost immune responses to cancer. These examples illustrate the potential of the emerging field of ‘glycomedicine’. Glycosylation refers to the addition of carbohydrate chains to proteins and lipids. In this Review, the authors discuss the broad role of glycans in immunity, cancer, xenotransplantation and glomerular filtration and the potential of ‘glycomedicine’.

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Glycosylation in health and disease.

Alkaloids mimicking the structures of monosaccharides are now believed to be widespread in plants and microorganisms, and these sugar mimics inhibit glycosidases because of a structural resemblance to the sugar moiety of the natural substrate. Naturally occurring sugar mimics with a nitrogen in the ring are classified into five structural classes: polyhydroxylated piperidines, pyrrolidines, indolizidines, pyrrolizidines and nortropanes. Glycosidases are involved in a wide range of important biological processes, such as intestinal digestion, post-translational processing of glycoproteins and the lysosomal catabolism of glycoconjugates. The realization that alkaloidal sugar mimics might have enormous therapeutic potential in many diseases such as viral infection, cancer and diabetes has led to increasing interest and demand for these compounds. Most of these effects can be shown to result from the direct or indirect inhibition of glycosidases. The glycosphingolipid (GSL) storage diseases are relatively rare hereditary disorders that are severe in nature and frequently fatal. Possible strategies for the treatment of these lysosomal storage diseases include enzyme replacement therapy, gene therapy and substrate deprivation. Recently, quite a new therapy for lysosomal storage diseases has been reported, namely a ‘chemical chaperone therapy’ for Fabry disease. In this report, the structural basis for the specificity of inhibition of alkaloidal sugar mimics and their current and potential application to biomedical problems will be reviewed.

Sugar-mimic glycosidase inhibitors: natural occurrence, biological activity and prospects for therapeutic application

About 40 years have passed since the classical glycosidase inhibitor nojirimycin was discovered from the cultured broth of the Streptomyces species. Since then, over 100 glycosidase inhibitors have been isolated from plants and microorganisms. Modifying or blocking biological processes by specific glycosidase inhibitors has revealed the vital functions of glycosidases in living systems. Because enzyme-catalyzed carbohydrate hydrolysis is a biologically widespread process, glycosidase inhibitors have many potential applications as agrochemicals and therapeutic agents. Glycosidases are involved in the biosynthesis of the oligosaccharide chains and quality control mechanisms in the endoplasmic reticulum of the N-linked glycoproteins. Inhibition of these glycosidases can have profound effects on quality control, maturation, transport, and secretion of glycoproteins and can alter cell-cell or cell-virus recognition processes. This principle is the basis for the potential use of glycosidase inhibitors in viral infection, cancer, and genetic disorders. In this review, the past and current applications of glycosidase inhibitors to agricultural and medical fields and the prospect for new therapeutic applications are reconsidered.

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Glycosidase inhibitors: update and perspectives on practical use.

A survey is given of the wide range of different materials and organisms that can be classified as biopesticides. Details are given of those currently of commercial importance, and future developments in this area are discussed. It is considered that, while in the immediate future biopesticides may continue to be limited mainly to niche and speciality markets, there is great potential for long-term development and growth, both in their own right and in providing leads in other areas of pest management science.

Biopesticides: a review of their action, applications and efficacy

6.1. Oxadiazoles 4154 6.2. Diazaphospholes 4154 7. Six-Membered Heterocycles with One Heteroatom 4155 7.1. Pyridines 4155 7.2. Pyridinones 4155 7.3. Quinolines 4156 7.4. Quinolinones 4157 7.5. Isoquinolines 4157 7.6. Acridines 4158 7.7. Pyranones 4158 7.8. Flavones 4159 8. Six-Membered Heterocycles with Two Heteroatoms 4159 8.1. Pyridazinones 4159 8.2. Pyrimidines 4159 8.3. Pyrimidinones 4160 8.4. Quinazolines 4162 8.5. Quinazolinones 4162 8.6. Quinoxalines 4164 8.7. Quinoxalinediones 4165 8.8. Oxazines 4165 8.9. Oxazinones 4166 8.10. Thiazines 4166 9. Six-Membered Heterocycles with Three Heteroatoms 4166

Solvent-free heterocyclic synthesis.

Various kinds of N-substituted valiolamine derivatives, including compounds 23a, 24a, and 34a, which are structurally analogous to the key pseudodisaccharides (25a and 26a) of naturally occurring oligosaccharide alpha-D-glucosidase inhibitors, have been synthesized and estimated by the measure of inhibitory activity against porcine sucrase and maltase. The N-substituted valiolamine derivatives evaluated in this study have been found to be more potent than the corresponding N-substituted valienamine derivatives as well as the parent valiolamine. It is noteworthy that even simple N-substituted valiolamine derivatives such as N-[2-hydroxy-1-(hydroxymethyl)ethyl]-, N-[(1R,2R)-2-hydroxycyclohexyl]-, and N-[(R)-(-)-beta-hydroxyphenethyl]valiolamine (6, 8a, and 9a) have the stronger alpha-D-glucosidase inhibitory activity against porcine intestinal maltase and sucrase than naturally occurring oligosaccharide alpha-D-glucosidase inhibitors.

Synthesis and alpha-D-glucosidase inhibitory activity of N-substituted valiolamine derivatives as potential oral antidiabetic agents.

Valiolamine, a new aminocyclitol has been isolated from the fermentation broth of Streptomyces hygroscopicus subsp. limoneus and its structure has been determined to be (1(OH),2,4,5/1,3)-5-amino-1-C-(hydroxymethyl)-1,2,3,4-cyclohexanetetr ol. Valiolamine has more potent alpha-glucosidase inhibitory activity against porcine intestinal sucrase, maltase and isomaltase than valienamine, validamine and hydroxyvalidamine which were reported as building blocks of validamycins and microbial oligosaccharide alpha-glucosidase inhibitors. In addition, valienamine, validamine and hydroxyvalidamine have been isolated from the fermentation broth.

Valiolamine, a new alpha-glucosidase inhibiting aminocyclitol produced by Streptomyces hygroscopicus.

Microbial degradation of validamycin A gave a new unsaturated aminocyclitol (5) with the 1S-configuration, establishing the structure (1) of the unsaturated cyclitol portion of validamycin A; the structure of epivalidamine (6), a new aminocyclitol derived from dihydrovalidamycin A was also elucidated.

The unsaturated cyclitol part of the new antibiotics, the validamycins

Studies on validamycins, new antibiotics. VI. Validamine, hydroxyvalidamine and validatol, new cyclitols.

This paper describes the isolation and characterization of four components of validamycin complex, validamycins C, D, E and F, in addition to validamycins A and B reported in the previous papers^40. Validamycins A, C, D, E and F are different from each other in the site and/or the type of glucosidic linkage to validoxylamine A5). The presence of validoxylamines A and B5) in the culture nitrate was also demonstrated.

Satoshi Horii

Papers

Synthesis and alpha-D-glucosidase inhibitory activity of N-substituted valiolamine derivatives as potential oral antidiabetic agents.

Valiolamine, a new alpha-glucosidase inhibiting aminocyclitol produced by Streptomyces hygroscopicus.

The unsaturated cyclitol part of the new antibiotics, the validamycins

Studies on validamycins, new antibiotics. VI. Validamine, hydroxyvalidamine and validatol, new cyclitols.

Studies on validamycins, new antibiotics. 8. Isolation and characterization of validamycins C,D,E and F.