Efficient glycosylation of unprotected sugars using sulfamic acid: A mild eco-friendly catalyst
摘要:
Sulfamic acid, a mild and environmentally benign catalyst has been successfully used in the Fischer glycosylation of unprotected sugars for the preparation alkyl glycosides. A diverse range of aliphatic alcohols have been used to prepare a series of alkyl glycosides in good to excellent yield. (C) 2011 Elsevier B.V. All rights reserved.
Substrate specificity in hydrolysis and transglucosylation by family 1 β-glucosidases from cassava and Thai rosewood
摘要:
Thai rosewood (Dalbergia cochinchinensis Pierre) dalcochinase and cassava (Manihot esculenta Crantz) linamarase are glycoside hydrolase family 1 beta-glucosidases with 47% amino acid sequence identity. Each enzyme can hydrolyze its natural substrate, dalcochinin-8'-O-beta-D-glucoside and linamarin, respectively, but not the natural substrate of the other enzyme. Linamarase can transfer glucose to primary, secondary and tertiary alcohols with high efficiency, while dalcochinase can transglucosylate primary and secondary alcohols at moderate levels. In this study, eight amino acid residues in the aglycone binding pocket of dalcochinase were individually replaced with the corresponding residues of linamarase, in order to identify residues that may account for their catalytic differences. The residues 1185 and V255 of dalcochinase appeared important for its substrate specificity, with their respective mutations resulting in 24- and 12-fold reductions in K-cat/K-m for the hydrolysis of dalcochinin-8'-O-beta-D-glucoside. Transglucosylation activity was improved when 1185, N189 and V255 of dalcochinase were replaced with A201, F205 and F271 of linamarase, respectively, suggesting these residues support transglucosylation in linamarase. Among these three mutants, only the N189F mutant showed significant increases in the rate constants for the reactivation of trapped glucosyl-enzyme intermediates by all alcohols. Together, our results suggest that both hydrophobicity and geometry are important determinants for substrate specificity in hydrolysis and transglucosylation by these family 1 beta-glucosidases. (C) 2010 Elsevier B.V. All rights reserved.
PROCEDE DE FABRICATION ENZYMATIQUE D'$g(a)-GLUCOSIDES ET D'ESTERS D'$g(a)-GLUCOSIDES, ET UTILISATIONS DES PRODUITS AINSI OBTENUS
申请人:ULICE S.A.
公开号:EP0605453A1
公开(公告)日:1994-07-13
Procédé de fabrication enzymatique d'alpha-glucosides et de leurs esters
申请人:ULICE S.A.
公开号:EP0605453B1
公开(公告)日:1997-01-08
US5773256A
申请人:——
公开号:US5773256A
公开(公告)日:1998-06-30
[EN] METHOD FOR THE ENZYMATIC PRODUCTION OF (ALPHA)-GLUCOSIDES AND ESTERS OF (ALPHA)-GLUCOSIDES, AND UTILIZATIONS OF PRODUCTS THUS OBTAINED
申请人:ULICE SA
公开号:WO1993004185A1
公开(公告)日:1993-03-04
(EN) The present invention relates to a method for the enzymatic production of $g(a)-glucosides, characterized by contacting at least one alcohol whose only functional group or groups is/are a hydroxyl group or groups, with starch, maltodextrines or maltose, in the presence of a purified enzymatic preparation having an $g(a)-transglucosylation activity. The invention relates also to an enzymatic method for the esterification of the $g(a)-glucosides thus obtained.(FR) La présente invention concerne un procédé de fabrication enzymatique d'$g(a)-glucosides, caractérisé par la mise en contact d'au moins un alcool dont le(s) seul(s) groupement(s) fonctionnel(s) est(sont) un(des) groupement(s) hydroxyl, avec de l'amidon, des maltodextrines ou du maltose, en présence d'une préparation enzymatique purifiée présentant une activité d'$g(a)-transglucosylation. L'invention concerne également un procédé enzymatique d'estérification des $g(a)-glucosides ainsi obtenus.