Competitive inhibition of the inverting beta-xylosidase of Bacillus pumilus 12 by monosaccharide derivatives of different structural and conformational types. A possible natural substrate.
The title enzyme is competitively inhibited by compounds, for example alpha-D-xylopyranosylpyridinium salts and 1,6-anhydro-D-glucopyranose, for which the normal 4C1 conformation of the xylopyranose ring is precluded. It is competitively inhibited by compounds, for example beta-D-xylopyranosylpyridinium salts and 1,6-anhydro-L-idopyranose, for which the 1C4 conformation is precluded, and which have no accessible conformations in common with the first set of inhibitors. It is also competitively inhibited by alpha-L-arabinofuranosides. Inhibition by 1,6-anhydroglucopyranose, 1,6-anhydro-L-idopyranose and L-arabinono-gamma-lactone is competitive with respect to each other. alpha-D-Xylopyranosyl fluoride is not a detectable substrate, by itself or in the presence of a representative of any of the three types of inhibitor. On the basis of these and literature data, it is proposed that the natural substrate is a hemicellulose fragment containing the D-Xylp beta (1 leads to 4)-[L-Araf alpha (1 leads to 3)]D-Xylp structure. Tentative inferences about the catalytic mechanism can also be drawn.
D001407:Bacillus / Q000201:enzymology*; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002384:Catalysis; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors*; D006027:Glycosides / Q000378:metabolism; D007700:Kinetics; D009005:Monosaccharides / Q000494:pharmacology*; D011726:Pyridinium Compounds / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D014995:Xylosidases / Q000037:antagonists & inhibitors*
D006027:Glycosides; D009005:Monosaccharides; D011726:Pyridinium Compounds; C008646:4-nitrophenyl beta-D-xyloside; D006026:Glycoside Hydrolases; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase