Conduritol B-epoxide

If k2 > kj, the glycosyl-enzyme intermediate will accumulate, and may be trapped by the rapid denaturation of the enzyme in the presence of (saturating) amounts of substrate. With -glucoside Aj from Asp. wentii and 4-nitrophenyl [ C]-2-deoxy-) -D-irra />jo-hexopyranoside, it was possible to identify the intermediate as a glycosyl ester (acylal) of 2-deoxy-D-arabino-hexose bound to the same aspartate residue that had previously been labeled with the active-site-directed inhibitor conduritol B epoxide and with D-glucal." This constituted an important proof that the carboxylate reacting with the epoxide is directly involved in catalysis. 

A. Nahrstedt, W. Hosel, and A. Walther, Phytochemistry, 18(1979) 1137-1141 Resistance of the /(-D-glucosidases of Refs. 151 and 152 against inactivation by conduritol B epoxide, W. H6sel, personal communication. 

The only other examples of bromoconduritol inhibition reported so far are a cytosolic jff-D-glucosidase from calf liver and the lysosomal ff-D-glu-cosidase from calf spleen. In spite of the 6500-fold difference in their reactivity with conduritol B epoxide (see Table XI), both enzymes are rapidly inactivated by bromoconduritol F, with kj(max)/Kj 10 M min for the cytosolic enzyme and lq(max)/Ki 3.2 10 for the crude and 3.9 10 M min for the purified lysosomal enzyme. It should be noted that purification of the lysosomal jS-D-glucosidase had effects on the reactivity with bromoconduritol F similar to those it had on the reactivity with conduritol B epoxide (see Table XI). 

L. Premkumar, A. R. Sawkar, S. Boldin-Adamsky, L. Toker, I. Sihnan, J. W. Kelly, A. H. Futerman, and J. L. Sussman, X-ray structure of human acid-p-glucosidase covalently bound to conduritol-B-epoxide,./. Biol. Chem., 25 (2005) 23815-23819. 

Unsurprisingly, the nitrogen analogue of conduritol epoxide inactivated GH 13 yeast ot-glucosidase and a GH 1 p-glucosidase from Agrobacterium faecalis the inactivation appeared faster than with conduritol B epoxide itself. 

Figure 5.33 (a) Labelling of glucosidases with the conduritol B epoxide, (b) Similar-... 

Glycals have been successfully used to tag active site amino acids. Denatur-ation of Aspergillus wentii )3-glucosidase Aj in the presence of D-glucal traps the hydrated product bound as an aspartate ester (62). The residue is apparently the same /8-glucosidase aspartic acid labeled with the site-directed irreversible inhibitor conduritol B epoxide (63, 64). 

Abbreviations CBE conduritol B-epoxide CSF cerebrospinal fluide CMT chaperon-mediated therapy CNS central nervous system ER endoplasmic reticulum ERAD endoplasmic reticulum associated degradation ERT ... 

Levels of D-glucosyl ceramidase in mice dropped very rapidly after conduritol B epoxide injection, reaching a minimum after 1 hr in liver.There was a noticeable restoration of activity within the next 2-3 hr. The level of aryl /3-D-glucosidase decreased somewhat less than that of cerebrosidase, reaching a minimum within 2 h it too showed some recovery of activity within 3 hr. 

Access to new cyclitol thiirane derivatives has been reported by reaction of cyclitol epoxides with dimethylthioformamide in trifluoroacetic acid. For example the episulfide analogue 90 was produced from the conduritol B epoxide compound 91. Several similar examples were described starting from cyclitol epoxides prepared by known methods. 

Legler, G. (1968) Investigations on the mechanism of action of glycoside-spUtting enzymes. 3. Labelling of the active centre of a P-glucosidase from aspeigillus wenti with (14C) conduritol B epoxide. Hoppe-Seyler s Z. Physiol Chem., 349,... 

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