Glycosidases oligosaccharide

Since the colonic bacterial enzymes are capable of hydrolyzing various di- and oligosaccharides (glycosidases) and polysaccharides (polysaccharidases), the chi-tosanolytic activities of rat cecal and colonic enzymes on chitosan was investigated. The results revealed that the rat bacterial enzymes have the ability to degrade chitosan, depending on both the Mw and DA of the chitosan sample [171]. 

We have used two types of enzymes for the production of oligosaccharides glycosidases (E.C. sub-class 3.2) and glycosyltransferases (E.C. sub-class 2.4) (9, 10). In this chapter we discuss the relative advantages and disadvantages of using each class of enzyme as a catalyst for the synthesis of complex carbohydrates. 

The structures of many oligosaccharide chains can be elucidated by gas-liquid chromatography, mass spectrometry, and high-resolution NMR spectrometry. Glycosidases hydrolyze specific linkages in oligosaccharides and are used to explore both the structures and functions of glycoproteins. 

A detailed study of the 0-linked oligosaccharides present on the surface of normal granulocytes, chronic myelogenous leukemia cells, and acute myelogenous leukemia cells has been completed. Structures were elucidated by f.a.b.-m.s. after permethylation, and methylation analysis before and after specific exo-glycosidase treatments. Some of the components were shown by f.a.b.-m.s. to be poly(N-acetyllactosaminyl) oligosaccharides, for example, 29. 

Moracci, M., Cobucci-Ponzano, B., Perugino, G. et al. (2005) Recent developments in the synthesis of oligosaccharides by hyperthermophilic glycosidases, in Handbook of Carbohydrate Engineering (ed. K.J. Yarema), CRC Press LLC, Boca Raton, FL, pp. 587-612. 

Nishio, T., Hakamata, W., Ogawa, M. et al. (2005) Investigations of a useful a-glycosidase for the enzymatic synthesis of rare sugar oligosaccharides. Journal of Applied Glycoscience, 52, 153-160. 

Oligosaccharide syntheses employing enzymatic reactions would in principle greatly benefit from being performed on a polymer support since the support might effectively facilitate isolation of the final product. Presumably, a water-soluble polymeric support will be preferable to any insoluble support since reaction rates could otherwise become too slow. Glycosidases as synthetic enzymes would be the best candidates to study this type of the enzymic approach to oligosaccharide synthesis. 

Pemsino, G., Cobucci-Ponzano, B., Rossi, M. and Moracci, M., Recent advances in the oligosaccharide synthesis promoted by catalytically engineered glycosidases. Adv. Synth. Catal.,... 

Singh, S. Scigelova, M. Crout, D. H. G., Glycosidase-catalysed synthesis of oligosaccharides A two-step synthesis of the core trisaccharide of N-hnked glycoproteins using the beta-N-acetylhexosaminidase and the beta-mannosidase from... 

Carbohydrates mainly occur in food in the form of polymers (starches and glycogen). They are cleaved by pancreatic amylase into oligosaccharides and are then hydrolyzed by glycosidases, which are located on the surface of the intestinal epithelium, to yield monosaccharides. Glucose and galactose are taken up into the enterocytes by secondary active cotransport with Na"" ions (see p. 220). In addition, monosaccharides also have passive transport systems in the intestine. 

There is a clear distinction between exo- and endo-glycosidases the former act at the nonreducing end of a glycan chain, whereas the latter cleave at some point along an oligosaccharide chain, either at random or in a chemical environment -specific manner. 

---