[Glycosides of amino sugars. 3. Synthesis of strophanthidin-3-(3'-amino-3'-deoxy- -glucopyranoside)].
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Amino Sugars↗
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Alternative route for biosynthesis of amino sugars in Escherichia coli K-12 mutants by means of a catabolic isomerase.
By inserting a lambda placMu bacteriophage into gene glmS encoding glucosamine 6-phosphate synthetase (GlmS), the key enzyme of amino sugar biosynthesis, a nonreverting mutant of Escherichia coli K-12 that was strictly dependent on exogenous N-acetyl-D-glucosamine or D-glucosamine was generated. Analysis of suppressor mutations rendering the mutant independent of amino sugar supply revealed that the catabolic enzyme D-glucosamine-6-phosphate isomerase (deaminase), encoded by gene nagB of the nag operon, was able to fulfill anabolic functions in amino sugar biosynthesis. The suppressor mutants invariably expressed the isomerase constitutively as a result of mutations in nagR, the locus for the repressor of the nag regulon. Suppression was also possible by transformation of glmS mutants with high-copy-number plasmids expressing the gene nagB. Efficient suppression of the glmS lesion, however, required mutations in a second locus, termed glmX, which has been localized to 26.8 min on the standard E. coli K-12 map. Its possible function in nitrogen or cell wall metabolism is discussed.
Aldose-Ketose Isomerases↗
Determination of methylated basic, 5-hydroxylysine, elastin crosslinks, other amino acids, and the amino sugars in proteins and tissues.
Analytical single-column chromatographic methods have been developed for determining all methylated basic amino acids, isodesmosine, desmosine, the amino sugars glucosamine and galactosamine, the diastereoisomers of 5-hydroxylysine, and related compounds at picomole levels in protein and tissue hydrolysates. Complete resolution of all these unique basic amino acids as discrete peaks was achieved in 5.4 on a 50 X 0.28-cm microcolumn of Dionex type DC-4A spherical resin (9.0 +/- 0.5 micron) using updated instrumentation commonly available for amino acid analysis. The column was operated at 5.65 ml/h with two 0.35 M sodium citrate buffers (pH 5.700 and 4.501), at two temperatures (31.5 and 73 degrees C). Excellent resolution of all omega-N-methylarginines and related compounds was also achieved in 3 h using a 17.5 X 0.28-cm microcolumn of Dionex DC-5A resin (sized to 6.0 +/- 0.5 microns), two citrate buffers (0.21 M Na+, pH 5.125; 0.35 M Na+, pH 5.700), a buffer flow rate of 5.75 ml/h, and a temperature of 52 degrees C. Complete separation of all other amino acids found in protein or tissue hydrolysates including S-carboxymethyl cysteine, 4-hydroxyproline, methionine S,S-dioxide, and the amino sugars was also carried out in 95 min using a 23.5 X 0.28-cm microcolumn of Dionex DC-5A resin. The use of purified microcolumn buffers gave smooth baselines without interference from artifacts or minor hydrolysate components. The major advantages of these methods are: first, their high resolving power; second, their high sensitivity which is comparable and in some aspects superior to the newer instruments; and third, their high reproducibility (100 +/- 2.5%) and low operating costs. These methods should be especially valuable for determining myosin, actin, and elastin in tissue hydrolysates from the amounts of N tau-methylhistidine, desmosine, or isodesmosine present, respectively, and for studying protein methylation, hydroxylation, cross-linking formation, and the turnover rates of contractile and connective tissue proteins in biological systems.
Amino Acids↗
AMINO SUGARS IN L FORMS OF BACTERIA AND PLEUROPNEUMONIA-LIKE ORGANISMS.
Sharp, John T. (Harvard Medical School, Boston, Mass.). Amino sugars in L forms of bacteria and pleuropneumonia-like organisms. J. Bacteriol. 86:692-701. 1963.-Studies of several bacterial L forms and their parent bacteria have revealed similar amino sugars in the two forms of microorganisms, with the exception that muramic acid was absent from the streptococcal and staphylococcal L forms. In contrast, muramic acid was found in a Proteus L form. Some of the properties of the muramic acid component in the Proteus L form are described. The solubility of this material was observed to be very different in the L form as compared with the bacterium. Some implications of this observation are discussed. Two strains of pleuropneumonia-like organisms did not contain muramic acid.
Amino Sugars↗
Sugar amino acids and their uses in designing bioactive molecules.
In search of new molecular entities for discovering new drugs and materials, organic chemists are looking for innovative approaches that try to imitate nature in assembling quickly large number of distinct and diverse molecular structures from 'nature-like' and yet unnatural designer building blocks using combinatorial approach. The main objective in developing such libraries is to mimic the diversities displayed in structures and properties of natural products. The unnatural building blocks used in these assemblies are carefully designed to manifest the structural diversities of the monomeric units used by nature like amino acids, carbohydrates and nucleosides to build its arsenal. Compounds made of such unnatural building blocks are also expected to be more stable toward proteolytic cleavage in physiological systems than their natural counterparts. Sugar amino acids constitute an important class of such polyfunctional scaffolds where the carboxyl, amino and hydroxyl termini provide an excellent opportunity to organic chemists to create structural diversities akin to nature's molecular arsenal. Recent advances in the area of combinatorial chemistry give an unprecedented technological support for rapid compilations of sugar amino acid-based libraries exploiting the diversities of carbohydrate molecules and well-developed solid-phase peptide synthesis methods. This review describes the development of sugar amino acids as a novel class of peptidomimetic building blocks and their applications in creating large number of structurally diverse peptide-based molecules many of which display interesting three-dimensional structures as well as useful biological properties.
Amino Acids↗
Selective DNA cleavage by elsamicin A and switch function of its amino sugar group.
We report guanine-specific recognition and selective cleavage of DNA by the antitumor antibiotic elsamicin A equipped with an amino sugar and compare these results with cleavage by chartarin and chartreusin antibiotics. The preferential cutting sites of DNA strand scission with elsamicin A are on the bases adjacent to the 3'-side of guanine residues such as 5'-GN sites, in particular 5'-GG sites. The present results also indicate that (1) the aglycon portion binds intercalatively to the 3'-side of guanine in host DNA, (2) the guanine 2-amino group has an important effect on selective DNA binding of elsamicin A, and (3) the amino sugar residue of elsamicin A facilitates the drug binding into the minor groove of B-DNA. In addition, we found that an acetylation of the amino group on the elsamicin A sugar portion plays an interesting switch function for the activity of elsamicin A. The biological implication of this switch has also been discussed.
Aflatoxin B1↗
Highly stereoselective synthesis and structural characterization of new amino sugar derivatives.
2-C-Nitroalkyl-1,4:3,6-dianhydromannitols were synthesized via a Henry reaction of nitroalkyls with 1,4:3,6-dianhydrofructose. Catalytic hydrogenation then afforded the corresponding vicinal amino alcohols. Oximation of 1,4:3,6-dianhydrofructose with hydroxylamine, followed by hydrogenation, gave 2-amino-1,4:3,6-dianhydro-2-deoxymannitol. All compounds were elucidated by their HRMS, 1H NMR, 13C NMR, and IR spectra. The absolute configurations of the amino sugar derivatives were confirmed by single-crystal X-ray analysis or NOESY spectral studies. The possible mechanism for hydrogenation of the nitro 2-C-nitroalkyl sugar is proposed. The conformations of the fused furan rings of nitro and amino sugar derivatives are presented.
Amino Sugars↗
Cp*Rh-based indicator-displacement assays for the identification of amino sugars and aminoglycosides.
Indicator-displacement assays based on the organometallic complex [{Cp*RhCl2}2] (Cp*=pentamethylcyclopentadienyl) and the dye gallocyanine were used to sense amino sugars and aminoglycosides in buffered aqueous solution by conducting UV-visible spectroscopy. The data of three assays at pH 7.0, 8.0, and 9.0 were sufficient to distinguish between the amino sugars galactosamine, glucosamine, mannosamine and the aminoglycosides kanamycin A, kanamycin B, amikacin, apramycin, paromomycin, and streptomycin. Furthermore, the assays were used to characterize mixtures of aminoglycosides and obtain quantitative information about the respective analytes.
Amino Sugars↗
Identification of amino sugars.
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Amino Sugars↗
Cyclic homooligomers from sugar amino acids: synthesis, conformational analysis, and significance.
Sugar amino acids (SAAs) were designed as new building blocks carrying an amino group and a carboxyl group on a carbohydrate scaffold. By exploiting standard solid- and solution-phase coupling procedures, linear and cyclic homooligomers containing glucosyluronic acid methylamine (Gum) were synthesized. We achieved a high yield and a very short coupling time for the oligomerization and cyclization of sequences encompassing two, three, four, and six Gum units. The synthesis of cyclic oligomers containing only SAAs as repetitive units has not been reported before. The conformational preferences in aqueous solution of the cyclic derivatives and their applications as potential host molecules are described herein. Benzoic acid and p-nitrophenol were chosen as model guest molecules to study the formation of cyclodextrin-like inclusion complexes. The complexation behavior of the cyclic hexamer was proved from three different points of view: chemical shifts, longitudinal relaxations (T(1)), and diffusion coefficients. All of them showed different values for host and guest molecules measured independently and in the presence of each other.
Amino Acids↗
Amino sugar sensitivity in Escherichia coli mutants unable to grow on N-acetylglucosamine.
Studies were conducted on two mutants of Escherichia coli that lack either glucosamine-6-phosphate deaminase or N-acetylglucosamine-6-phosphate deacetylase and which accumulate glucosamine-6-phosphate or N-acetylglucosamine-6-phosphate, respectively, when grown in the presence of N-acetylglucosamine. The addition of 10(-4) to 10(-5)mN-acetylglucosamine to these mutant strains caused a rapid and complete inhibition of growth on substrates that enter the catabolic pathways at or below the level of fructose-6-phosphate. Growth on glucose was inhibited to a lesser degree, whereas only minor inhibition occurred when the pentoses were used as substrates. Growth on gluconate was found to be totally unaffected by these levels of N-acetylglucosamine. The objective of this investigation was to determine the nature of this "amino sugar sensitivity" phenomenon and the conditions under which it could be overcome. It was found that this amino sugar sensitivity was abolished when an exogenous source of pentose such as uridine was included in the culture medium. Experiments are described indicating that the accumulated amino sugar phosphate metabolites interfere with an early step in hexose metabolism of both mutants, resulting in a pentose deficiency and consequent inhibition of growth on certain substrates.
Amidohydrolases↗
[Effect of diet and microflora on amino sugars in the digestive contents and faeces of rats, lambs and preruminant calves].
Glucosamine (Glc NH2) and galactosamine (Gal NH2) were determined by an automatized chromatographic method in samples from digestive contents and faeces. Germfree lambs and rats as well as conventional preruminant calves, lambs and rats were used in the experiments. The rats were fed an irradiated casein diet, the lambs UHT milk and the preruminant calves various diets (table 1). Concentrations of Glc NH2 and of Gal NH2 reached 6 g/16 g of N in the caecal contents and the faeces of germfree rats (table 2). Concentrations of Gal NH2 were 7 to 12 times lower and those of Glc NH2 4 times lower in conventional rats. In lambs, the amino sugar concentrations (table 3) found in the stomach contents resembled those supplied by the milk. In contrast, in the large intestine and the faeces, the concentration of amino sugars was very high. In conventional lambs, those concentrations were 8 to 4 times lower. For ruminant calves, the concentrations of amino sugars (table 4) were greater in the ileal contents than in the faeces. They reached that of meconium when the calves were fed milk. The lowest values were observed in the faeces of calves fed soya, colostrum or fish diets which are less digestible than milk. In germfree animals, the hexosamines were endogenous. In conventional animals, bacterial metabolism led to an increase in faecal Glc NH2/Gal NH2. In the calves fed soya or fish diets, the hexosamine content in the faeces was low owing to the dilution of bacterial and endogenous mucoproteins by the undigested dietary proteins.
Animals↗
Sugar amino acid based scaffolds--novel peptidomimetics and their potential in combinatorial synthesis.
To meet the growing demands for the development of new molecular entities for discovering new drugs and materials, organic chemists have started looking for new concepts to supplement traditional approaches. In one such approach, the expertise gained over the years in the area of organic synthesis and the rational drug-design concepts are combined together to create "nature-like" and yet unnatural organic molecules that are expected to provide leads in discovering new molecules. Emulating the basic principles followed by nature to build its vast repertoire of biomolecules, organic chemists are developing many novel multifunctional building blocks. Sugar amino acids constitute an important class of such polyfunctional scaffolds where the carboxyl, amino and hydroxyl groups provide an excellent opportunity for organic chemists to create structural diversities akin to nature's molecular arsenal. Recent advances in the area of combinatorial chemistry give unprecedented technological support for rapid compilations of sugar amino acid-based libraries exploiting the diversities of carbohydrate molecules and well-developed solid-phase peptide synthesis methods. This review chronicles the development of sugar amino acids as a novel class of peptidomimetic building blocks and their applications in generating desired secondary structures in peptides as well as in creating mimics of natural biopolymers.
Amides↗
Isolation of a new amino sugar from Chromobacterium violaceum.
Smith, E. J. (Duke University, Durham, N.C.), J. M. Leatherwood, and R. W. Wheat. Isolation of a new amino sugar from Chromobacterium violaceum. J. Bacteriol. 84:1007-1010. 1962.-An investigation of the amino sugars and reducing compounds of a lipopolysaccharide of Chromobacterium violaceum revealed the presence of a previously unreported cationic reducing compound. Evidence indicates that the compound is a 6-deoxyhexosamine with an amino group at other than the C-2 position.
Chromobacterium↗
Amino sugars in the glycoprotein toxin from Bacillus thuringiensis subsp. israelensis.
The carbohydrate content of purified Bacillus thuriniensis subsp. israelensis crystal toxin was determined by six biochemical tests, column chromatography on an amino acid analyzer, and the binding of 11 fluorescent lectins. The crystals contained approximately 1.0% neutral sugars and 1.7% amino sugars. The amino sugars consisted of 70% glucosamine and 30% galactosamine. No N-acetylneuraminic acid (sialic acid) was detected. The presence of amino sugars was confirmed by the strong binding of fluorescent wheat germ agglutinin and the weak binding of fluorescent soybean agglutinin. These lectins recognize N-acetyl-D-glucosamine and N-acetyl-D-galactosamine, respectively. The lectin-binding sites appeared evenly distributed among the protein subunits of the crystal. The sugars were covalently attached to the crystal toxin because wheat germ agglutinin still bound alkali-solubilized toxin which had been boiled in sodium dodecyl sulfate, separate by polyacrylamide gel electrophoresis, and transferred to nitrocellulose membranes. This study demonstrates the covalent attachment of amino sugars and indicates that the B. thuringiensis subsp. israelensis protein toxins should be viewed as glycoprotein toxins. The crystals used in the present study were purified on sodium bromide density gradients. Studies employing crystals purified on Renografin density gradients can give artificially high values for the anthrone test for neutral sugars.
Bacillus thuringiensis↗
Conformational analysis of furanoid epsilon-sugar amino acid containing cyclic peptides by NMR spectroscopy, molecular dynamics simulation, and X-ray crystallography: evidence for a novel turn structure.
Sugar amino acids (SAAs) are useful building blocks for the design of peptidomimetics and peptide scaffolds. The three-dimensional structures of cyclic hybrid molecules containing the furanoid epsilon-SAA III and several amino acids were elucidated to study the preferred conformation of such an epsilon-SAA and its conformational influence on the backbone of cyclic peptides. NMR-based molecular dynamics simulations and empirical calculations of the cyclic tetramer 1, consisting of two copies of the SAA residue and two amino acids, revealed that it is conformationally restrained. The two SAA residues adopt different conformations. One of them forms an unusual turn, stabilized by an intraresidue nine-member hydrogen bond. The methylene functionalities of the other SAA residue are positioned in such a way that an intraresidue H bond is not possible. The X-ray crystal structure of 1 strongly resembles the solution conformation. Molecular dynamics calculations in combination with NMR analysis were also performed for compounds 2 and 3, which contain the RGD (Arg-Gly-Asp) consensus sequence and were previously shown to inhibit alpha(IIb)beta(3)-receptor-mediated platelet aggregation. The biologically most active compound 2 adopts a preferred conformation with the single SAA residue folded into the nine-member H bond-containing turn. Compound 3, containing an additional valine residue, as compared with compound 2, is conformational flexible. Our studies demonstrate that the furanoid epsilon-SAA III is able to introduce an unusual intraresidue hydrogen bond-stabilized beta-turn-like conformation in two of the three cyclic structures.
Amino Acids↗
[Mechanism of polyene antibiotic inactivation. The effect of amino sugar oxidation on polyene chain destruction].
Changes in the acid-base characteristics of levorin during its inactivation are discussed. It is shown that with a decrease in the biological activity a change in the basic characteristics of the levorin amino sugar moiety takes place. The kinetic studies with model compounds, i. e. octaenic alcohol and glucosamine showed that the processes of their oxidation were interrelated. Oxidation of the amino sugar played the role of an inducing factor in oxidation of the polyenic chromophore and in addition impaired correlation between the extinction specific coefficient of levorin and its biological activity.
Amino Sugars↗
Transport of N-acetyl-D-galactosamine in Escherichia coli K92: effect on acetyl-amino sugar metabolism and polysialic acid production.
The N-acetyl-D-galactosamine (GalNAc) transport system of Escherichia coli K92 was studied when the bacterium was grown in a chemically defined medium containing GalNAc as a carbon source. Kinetic measurements were carried out in vivo at 37 degrees C in 25 mM phosphate buffer, pH 7.0. Under these conditions, the uptake rate was linear for at least 3 min and the calculated Km for GalNAc was 3 microM. The transport system was strongly inhibited by sodium arsenate (70%), potassium cyanide (62%) and 2,4-dinitrophenol (75%). Analysis of bacterial GalNAc phosphotransferase activity revealed in vitro GalNAc phosphorylation activity only when phosphoenolpyruvate was present. These results strongly support the notion that GalNAc uptake depends on a specific phosphotransferase system. Study of activity regulation showed that N-acetylglucosamine and mannosamine specifically inhibit the transport of GalNAc in this bacterium. Analysis of expression revealed that the GalNAc transport system is specifically induced by GalNAc but not by N-acetylglucosamine (GlcNAc) or N-acetylmannosamine (ManNAc), two intimately related sugars. Moreover, full induction of GalNAc transport required the presence of both cAMP and GalNAc. Comparative studies revealed that E. coli K92 has developed a regulation mechanism that specifically induces the appropriate permease based on the presence of each respective phospho-amino sugar (GlcNAc, ManNAc and GalNAc). In this regulation system, GlcNAc is the preferred amino sugar as the carbon source. Finally, when E. coli K92 was grown using GalNAc, capsular polysialic acid production was strongly affected. The presence of intracellular phosphoderivative acetylamino sugars, generated by the action of the phosphotransferase transport system, can be responsible for this effect.
Acetylgalactosamine↗