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Titolo:
GLUCOSIDASE-CATALYZED HYDROLYSIS OF ALPHA-D-GLUCOPYRANOSYL PYRIDINIUMSALTS - KINETIC EVIDENCE FOR NUCLEOPHILIC INVOLVEMENT AT THE GLUCOSIDATION TRANSITION-STATE
Autore:
HUANG XC; TANAKA KSE; BENNET AJ;
Indirizzi:
SIMON FRASER UNIV,DEPT CHEM BURNABY BC V5A 1S6 CANADA SIMON FRASER UNIV,DEPT CHEM BURNABY BC V5A 1S6 CANADA
Titolo Testata:
Journal of the American Chemical Society
fascicolo: 46, volume: 119, anno: 1997,
pagine: 11147 - 11154
SICI:
0002-7863(1997)119:46<11147:GHOAP>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
LONE-PAIR HYPOTHESIS; GLYCOSIDE HYDROLYSIS; BETA-GALACTOSIDASE; ENZYME INTERMEDIATE; ESCHERICHIA-COLI; AMP NUCLEOSIDASE; LEAVING GROUP; MECHANISM; ACID; INHIBITORS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
44
Recensione:
Indirizzi per estratti:
Citazione:
X.C. Huang et al., "GLUCOSIDASE-CATALYZED HYDROLYSIS OF ALPHA-D-GLUCOPYRANOSYL PYRIDINIUMSALTS - KINETIC EVIDENCE FOR NUCLEOPHILIC INVOLVEMENT AT THE GLUCOSIDATION TRANSITION-STATE", Journal of the American Chemical Society, 119(46), 1997, pp. 11147-11154

Abstract

Kinetic isotope effects (KIEs) on the yeast alpha-glucosidase-catalyzed hydrolysis of two alpha-D-glucopyranosyl pyridinium salts were measured at 25 degrees C and pH = 6.8. The measured KIEs on k(cat) for theH-2-2, C-13-1, and N-15-1' labeled substrates alpha-D-glucopyranosyl pyridinium bromide (1) and alpha-D-glucopyranosyl isoquinolinium bromide (2) were, respectively, 1.115 +/- 0.006 and 1.106 +/- 0.009, 1.028 /- 0.006 and 1.027 +/- 0.005, and 1.019 +/- 0.007 and 0.985 +/- 0.005. KIEs for the spontaneous hydrolysis of alpha-D-glucopyranosyl 4'-bromoisoquinolinium bromide (3) were measured at 80 degrees C and pH = 6.8, The measured KIEs on k(hyd) for the H-2-1, H-2-2, C-13-1, and N-15-1' labeled substrate alpha-D-glucopyranosyl 4'-bromoisoquinolinium bromide (3) were, respectively, 1.189 +/- 0.009, 1.094 +/- 0.010, 1.005 +/- 0.002, and 1.015 +/- 0.004. The KIEs obtained in this study of yeast alpha-glucosidase-catalyzed hydrolysis reactions are consistent witha transition state which involves a small degree of nucleophilic attack by an enzyme active site carboxylate group at the anomeric carbon center, whereas the corresponding transition state for the uncatalyzed reaction in water does not involve any nucleophilic assistance. In addition, the equilibrium isotope effects for deprotonation of the conjugate acid (K-a(14)/K-a(15)) of isoquinoline was measured to be 1.0216 +/- 0.0005.

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Documento generato il 18/09/20 alle ore 17:01:09