Abstract
A new class of inhibitors for beta -D-glycoside hydrolases, in which a single alpha-(1 -->4)-glycosidic bond is incorporated into an otherwise all-beta-(1 -->4)-linked oligosaccharide, is described. Such mixed beta/alpha -linkage cellooligosaccharides are not transition-state mimics, but instead are capable of utilising binding energy from numerous subsites, spanning either side of the catalytic centre, without the need for substrate distortion. This binding is significant; a mixed alpha/beta -D-tetrasaccharide acts competitively on a number of cellulases, displaying inhibition constants in the range of 40-300 muM. Using the Bacillus agaradhaerens enzyme Cel5A as a model system, one such mixed beta/alpha -cellooligosaccharide, methyl 4'',4'''-dithio-alpha -cellobiosyl-(1 -->4)-beta -cellobioside, displays a K-i value of 100 muM, an inhibition at least 150 times better than is observed with an equivalent all-beta -linked compound. the three-dimensional structure of B. agaradhaerens Cel5A in complex with methyl 4'',4'''-dithio-alpha -cellobiosyl-(1 -->4)-beta -cellobioside has been determined at 1.8 Angstrom resolution. This confirms the expected mode of binding in which the ligand, with all four pyranosides in the C-4(1) chair conformation, occupies the -3, -2 and +1 subsites whilst evading the catalytic (-1) subsite. Such "by-pass" compounds offer great scope for the development of a new class of beta -D-glycoside hydrolase inhibitors.
| Original language | English |
|---|---|
| Pages (from-to) | 319-325 |
| Number of pages | 7 |
| Journal | Chembiochem |
| Volume | 2 |
| Issue number | 5 |
| Publication status | Published - 4 May 2001 |
Keywords
- carbohydrates
- hydrolases
- inhibitors
- protein structures
- thiooligosaccharides
- SEQUENCE-BASED CLASSIFICATION
- ANGSTROM RESOLUTION
- HUMICOLA-INSOLENS
- ENDOGLUCANASE-I
- CYCLODEXTRIN GLYCOSYLTRANSFERASE
- MACROMOLECULAR STRUCTURES
- FUSARIUM-OXYSPORUM
- CRYSTAL-STRUCTURE
- ALPHA-AMYLASE
- MECHANISMS