A -Mannosidases

For example, prior action of GIcNAc transferase I is necessary for the action of Golgi a-mannosidase II. 

Colgate, S. M., Dorling, P. R. and Huxtable, C. R. 1979. A spectroscopic investigation of swainsonine an a-mannosidase inhibitor isolated from Swainsona canescens. Austral. J. Chem. 32 2257-2264. 

Base-catalyzed nitromethane cyclization of the dialdehyde generated by periodate oxidation of 1,2-O-cyclohexylidene-myo-inositol affords the nitrodiol with 1,4/2,3,5-configuration. This is converted into the a-mannosidase inhibitor, mannostatin A (Eq. 3.60).98... 

Cycloaddition reaction of nitrone (—)-(394) with dimethyl maleate D14 has been used for the synthesis of two new polyhydroxyl pyrrolizidines (687) and (688) (Schemes 2.293, 2.294). These compounds are analogs of alkaloids ros-marinecine and crotanecine, which were assayed for their inhibitory activities toward 22 commercially available glycosidase enzymes. One of them ((-)- a-epi-crotanecine) (—)-(688) is a potent and selective inhibitor of a-mannosidases (310). The reaction of (—)-(394) with dimethyl maleate gave a 9.6 6 1 mixture of cycloadducts (—)-(680), (+ )-(680), and (—)-(681), which arise from anti-exo,... 

Abbreviations. a-M, a-mannosidase AP, acid phosphatase as-ni-ATPase, anion-stimulated, nitrate-inhibitable ATPase CCR, NAD(P)H-dependent cytochrome oreduc-tase cs-vi-ATPase, cation-stimulated, vanadate-inhibitable ATPase, CAT, catalase GS 1/11, glucan synthase 1 or 11 IDPase, inosine diphosphatase cs-PPase, cation-stimulated pyrophosphatase RNA polymerase, DNA-dependent RNA polymerase TP-25, 25 kDa tonoplast integral protein. 

Substrate a-Mannosidase (human liver) j3-Mannosidase (human liver)... 

Since then it has been established that emulsin is a mixture of enzymes comprising in addition to /3-glucosidase28 the enzymes a-galactosidase, a-mannosidase, /3-glucuronidase and /3-(N-acetyl)-glucosaminidase. Concerning the process of purification of the Rohferment and the mode of differentiation of the constituent enzymes of emulsin, the most informa-... 

Swainsonine (1) is of great biochemical interest since it is a potent and specific inhibitor of both lysosomal a-mannosidase and mannosidase II, which are involved in the cellular degradation of polysaccharides and in the processing of asparagine-linked glycoproteins, respectively [1]. 

Figure 2.13 The indolizidine alkaloid toxin swainsonine (a potent inhibitor of a-mannosidase), responsible for locoweed toxicosis.

Genetic mannosidosis has been described in man, Angus cattle and Murray Gray cattle, and is characterized by a deficiency of a-mannosidase leading to storage of excess mannose-rich oligosaccharides in lysosomes. Pathologically, there is vacuolation of reticuloendothelial cells in the liver and lymph nodes, pancreatic exocrine cells, and neurons. Affected cattle are ataxic, uncoordinated, fail to thrive, and die in the first year of life. 

Fig. 23. Methyl a-septanoside mono-, di-, and tri-saccharides 243-245 assayed against jack-bean a-mannosidase.

M. A. Boone, F. E. McDonald, J. Lichter, S. Lutz, R. Cao, and K. I. Hardcastle, 1,5-a-D-Mannosepta-nosides, ring-size isomers that are impervious to a-mannosidase-catalyzed hydrolysis, Org. Lett., 11 (2009) 851-854. 

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