Four orders of magnitude rate increase in artificial enzyme-catalyzed aryl glycoside hydrolysis.
[reaction: see text] (6AR,6DR)-6A,6D-Di-C-cyano-beta-cyclodextrin (1) and 6A,6D-di-C-cyano-alpha-cyclodextrin (2) were synthesized and shown to catalyze hydrolysis of aryl glycosides into glucose and phenol with a reaction following Michaelis-Menten kinetics. At pH 8.0 and 59 degrees C hydrolysis of 4-nitrophenyl alpha-glucopyranoside was catalyzed by 1 with KM = 10.5 +/- 1.5 mM, kcat = 1.42(+/-0.09) x 10(-4) s(-1), and kcat/kuncat = 7922. Catalysis was observed with a concentration of 1 as low as 10 microM. Hydrolysis of the other aryl glycosides containing stereochemical variation in the sugar-moiety and 4-nitro-, 2-nitro-, 2-aldehydo-, and 2,4-dinitro- were also catalyzed by 1 and 2 with kcat/kuncat ranging from 4 to 7100. Hydrolysis of a phenyl beta-d-glucoside or the thioglycoside tolylthio beta-D-glucoside was also catalyzed. From a series of prepared analogues of 1 it was found that the catalysis was associated with the hydroxyl groups alpha to the nitril groups. The monocyanohydrin 6-C-cyano-beta-cyclodextrin (3) was also found to catalyze the hydrolysis of 4-nitrophenyl beta-glucopyranoside with kcat/kuncat = 1356. It was proposed that the cyclodextrin cyanohydrins 1-3 catalyze the hydrolysis by general acid catalysis on the bound substrate.
Ortega-Caballero
Fernando
F
Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Bjerre
Jeannette
J
Laustsen
Line Skall
LS
Bols
Mikael
M
D002384:Catalysis; D003505:Cyclodextrins / Q000138:chemical synthesis* / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008968:Molecular Conformation
D003505:Cyclodextrins; D006027:Glycosides