Journal of Applied Glycoscience
Online ISSN : 1880-7291
Print ISSN : 1344-7882
ISSN-L : 1344-7882
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Suicide Substrate-based Inactivation of Endodextranase by ω-Epoxyalkyl α-D-Glucopyranosides
Hee-Kwon KangYoung-Min KimHiroyuki NakaiMin-Sun KangWataru HakamadaMasayuki OkuyamaHaruhide MoriToshiyuki NishioAtsuo Kimura
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2010 Volume 57 Issue 4 Pages 269-272

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Abstract

Three kinds of ω-epoxyalkyl α-glucopyranosides (3′,4′-epoxybutyl α-D-glucopyranoside (E4G), 4′,5′-epoxypentyl α-D-glucopyranoside (E5G) and 5′,6′-epoxyhexyl α-D-glucopyranoside (E6G)), having alkyl chains of different lengths at their aglycone moieties, inactivated the endodextranase from Streptococcus mutans ATCC 25175 (SmDex) irreversibly with the pseudo-first order kinetics. Alkyl chain length-dependent inactivation was observed and the degree of activity loss was E5G, E6G and E4G, in that order, implying that the distance between epoxide group and glucosyl residue of ω-epoxyalkyl α-glucopyranoside was important in the modification of endodextranase. Inactivation by E5G followed the model of reversible intermediate-complex formation mechanism (suicide inhibitor-based mechanism). The rate constant of irreversible inactivation (k) and the dissociation constant of intermediate-complex (KR) of SmDex and E5G were 0.44 min-1 and 1.45 mM, respectively. Hydrolytic reaction product (isomaltose) protected SmDex from E5G-inactivation, suggesting that E5G bound to the catalytic site of SmDex. This is the first report that ω-epoxyalkyl α-glucopyranoside becomes a suicide substrate for endodextranase.

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© 2010 by The Japanese Society of Applied Glycoscience
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