Exo-glycosidases

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. 

Due to the extreme variety of xylan structures, it is obvious that many kinds of enzymes are needed for their complete hydrolysis in nature. Xylanases (EC 3.2.1.8.) are the polysaccharide hydrolases responsible for the attack of the polymer backbone itself. The total hydrolysis or modification of heteroxylans requires in addition several different exo-glycosidases and esterases. The present knowledge of these enzymes is reviewed in this paper. 

Exo-glycosidases Endo-glycosidases Glycos)mthases Transglycosylation Reverse hydrolysis Regio- and stereoselectivity... 

Thus, there appears to be an interlocking directorate with dynamic reciprocity for the various components of HA deposition that responds to the immediate needs of the cell. A tightly associated complex, termed the hyaluronasome, that contains HA receptors, the HA synthases, hyaluronidases, their respective inhibitors, exo- -glycosidases, as well as a spectrum of HA-binding proteins may constitute such an organelle. 

Figure 21 Chemical probes for monitoring glycan-processing enzymes, (a) Mechanism-based probe for labeling active exo-glycosidases in cell lysates/ (b) FRET-based reporter for OGT activity in cells. ...

Enzyme Inhibition - 2-Acetamido-2-deoxy-D-glucopyranose, chitobiose and chitotriose were P-glycosidically linked to various exo-glycosidase inhibitors, and evaluated as chitinase inhibitors. Good inhibition was found for an JV-formyl-pyrrolidine analogue (transition state mimic) and epoxybutyl chitobioside (an irreversible inhibitor). ... 

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