Polysaccharide, synthesis

In 1947, L-rhamnose was first recognized by Stacey as a constituent of Pneumococcus Type II specific polysaccharide. This finding was confirmed, in 1952, by Kabat et al. and in 1955 again by Stacey when 2,4- and 2,5-di-O-methyl-L-rhamnose were synthesized and the former was shown to be identical with a di-O-methylrhamnose, obtained by hydrolysis of the methylated polysaccharide. This result indicated a pyranose ring structure for the rhamnose units in the polysaccharide. Announcement of the identification of D-arabinofuranose as a constituent of a polysaccharide from M. tuberculosis aroused considerable interest. The L-enantiomer had been found extensively in polysaccharides, but reports of the natural occurrence of D-arabinose had been comparatively rare. To have available reference compounds for comparison with degradation products of polysaccharides, syntheses of derivatives (particularly methyl ethers) of both d- and L-arabinose were reported in 1947. 

Polysaccharides Synthesized by Micro-organisms. I. The Molecular Structure of Mannocaralose Produced from Glucose by Penicillium charlesii G. Smith, W. N. Haworth, H. Raistrick, and M. Stacey, Biochem. J., 29 (1935) 612- 621. 

The Structure of a Polysaccharide Synthesized by a Streptococcus Isolated from a Ropy Fermentation, The Value of Infrared Spectroscopy in Polysaccharide Studies, S. A. Barker, F. Pautard, I. R. Siddiqui, and M. Stacey, Chem. Ind. (London), (1955) 1450-1451. 

Leloir showed uridine diphosphate sugars needed for polysaccharide syntheses. 

Polysaccharides. Syntheses, Modihcations and Structure/Property Relations by... 

Functionally, starch can be considered as a polysaccharide synthesized in a manner permitting its efficient degradation. Hence, biosynthesis of the starch granule is a delicate balance between efficient packing of the glucan chains and the possibility of breaking these structures at degradation. To complete this enzymatically catalyzed process in the potato tuber, a multitude of different enzyme activities are required. 

Dimethyl-D-mannose has been isolated from the hydrolysis products of the methylated galactomannans from carob seed gum14-18 and from guar gum,16 17 and also from mannocarolose,8t 18 a polysaccharide synthesized by Penicillium charlesii G. Smith. The synthesis of this sugar, which has not been obtained crystalline, has been accom-... 

The monosaccharide composition of the products of the alkalii saponification of cellulose tosylates containing tosyloxy groups at Cg has been established on the basis of data obtained from a study of the composition of the products of acetylation, nitration, and periodate oxidation, and from quantitative paper chromatography of the products of complete hydrolysis of the mixed polysaccharides synthesized. The content of 3,6-anhydroglucose units in the 3,6-anhydro derivatives of cellulose was found to be 50-70 mol.-% (10-13). 

Dextrans are polysaccharides composed of linear glucose residues. They are produced from a polysaccharide synthesized by the bacteria Leuconostoc mesenteroides grown on sucrose media. Dextrans... 

From a study of 2,3-anh.ydro derivative of cellulose by infrared spectroscopy combined with the determination of the monosaccharide composition of the products of its acetylation and interaction with sodium methylate, we conclude that the mixed polysaccharide synthesized contains glucose and 2,3-anhydromannose units. 

The polysaccharide synthesized from a-n-glucosyl phosphate by P-enzyme resembles native amylose in several respects for example, it is sparingly soluble in water, and gives an intense blue color with iodine. The presence of (1—v4)-linked o-n-glucose residues was shown by the methylation study of Haworth and his coworkers, and the isolation of... 

The properties of polysaccharides synthesized from a-n-glucosyl phosphate by P- and Q-enzyme are shown in Table IV, and are related to the relative proportions of the two enzymes. An excess of either P- or Q-... 

In spite of the progress that has been made, several difficulties limit the use of cell-free enzymes for the synthesis of polysaccharides. The major problem is the complexity of many polysaccharide-synthesizing systems. Isolation, purification, and stabilization of the required enzymes is often difficult, as many enzymes lose activity when they are no longer membrane-associated. Enzyme isolation from eukaryotic sources is tedious, because of low cellular enzyme concentration. It is unlikely that cell-free enzymatic synthesis will provide better routes to most natural polysaccharides than do fermentation and isolation. The use of genetic engineering,... 

Yalpani, M. Polysaccharides Syntheses, Modifications and Structure/ Property Relations, Elsevier Amsterdam, 1988. 

Chemistry of Hetrocyclic Compounds edited by J. Kov4c and P. Z lupskjf Polysaccharides, Syntheses, Modifications and Structure/Property Relations by... 

Besides application to the analysis of polysaccharides of unknown structure, enzymes are also often used for routine measurements on polysaccharides of essentially established structure, such as the starch components and the glycogens. Enzymes provide extremely quick and accurate information for the characterization of polysaccharides of this type, including the products synthesized in vitro diuring studies on their mechanism of biosynthesis. There is also increasing application to the characterization of other types of polysaccharide, synthesized enzymically in vitro. A further important use is for investigation of the nature of the products formed by the action of other catabolic enzymes on polysaccharides such applications may give information on either the structure of the polysaccharide or the specificity of the catabolic enzyme under investigation. 

Nishimura, S., Kohgo, O., Kurita, K., and Kuzuhara, H. 1991. Chemospecific manipulations of a rigid polysaccharide Syntheses of novel chitosan derivatives with excellent solubility in common organic solvents by regioselective chemical modifications. Macromolecules 24 4745-4748. 

The production of D-glucose-1-phosphate as an intermediate does not seem to be necessary in other polysaccharide syntheses. Cane sugar (sucrose, saccharose), for example, is converted by the action of the enzyme dextran saccharase into dextran, a poly(glucose), with fructose as by-product. Another product of saccharose is levane, a poly(fructose) produced by the action of the enzyme levane saccharase through release of glucose. 

In general, it is possible to obtain higher degrees of polymerization by ring-opening polymerization than with polycondensation. Two types are used in oligo and polysaccharide syntheses orthoester synthesis and cationic anhydrosugar polymerization. 

---