General-acid and general-base catalysis of the cleavage of .alpha.-D-glucopyranosyl fluoride

Banait, Narinder S.; Jencks, William P.

doi:10.1021/ja00021a022

Cited by 69 publications

(76 citation statements)

References 4 publications

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“…89,90 Related solution reactions can also proceed with or without the formation of a discrete oxycarbenium intermediate. 91,92 The suggestion that the transition states for several enzymatic phosphoryl transfer reactions are similar to their solution counterparts is consistent with the expectation that less energy is required to stabilize a solution-like transition state than a substantially altered transition state (see Figure 1C,D; |∆∆G 1 q | > |∆∆G 2 q |). The data obtained in this work suggest that even an active site that is optimized for a loose transition state does not alter the transition state for a reaction that proceeds through a tighter transition state in solution.…”

Section: Resultssupporting

confidence: 79%

Alkaline Phosphatase Mono- and Diesterase Reactions: Comparative Transition State Analysis

2006

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Enzyme-catalyzed phosphoryl transfer reactions have frequently been suggested to proceed through transition states that are altered from their solution counterparts. Previous work with Escherichia coli alkaline phosphatase (AP), however, suggests that this enzyme catalyzes the hydrolysis of phosphate monoesters through a loose, dissociative transition state, similar to that in solution. AP also exhibits catalytic promiscuity, with a low level of phosphodiesterase activity, despite the tighter, more associative transition state for phosphate diester hydrolysis in solution. Because AP is evolutionarily optimized for phosphate monoester hydrolysis, it is possible that the active site environment alters the transition state for diester hydrolysis to be looser in its bonding to the incoming and outgoing groups. To test this possibility, we have measured the nonenzymatic and AP-catalyzed rate of reaction for a series of substituted methyl phenyl phosphate diesters. The values of beta(lg) and additional data suggest that the transition state for AP-catalyzed phosphate diester hydrolysis is indistinguishable from that in solution. Instead of altering transition state structure, AP catalyzes phosphoryl transfer reactions by recognizing and stabilizing transition states similar to those in aqueous solution. The AP active site therefore has the ability to recognize different transition states, a property that could assist in the evolutionary optimization of promiscuous activities.

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Section: Resultssupporting

confidence: 79%

Alkaline Phosphatase Mono- and Diesterase Reactions: Comparative Transition State Analysis

2006

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“…The HEPPSO O5 was also close to the KTGGL motif loop and makes a 2.9-Å hydrogen bond with the Leu-19 backbone amide. The sulfonic acid end of [13][14][15][16][17][18][19][20] in dmGS (yellow) and wtGSb (red) and the equivalent loop 14 -24 in the UDP/imidazole/Glu-6-P-bound OtsA (green, PDB 1gz5) and UDP-Glc-bound OtsA (blue, PDB 1uqu). The coil preceding and the helix subsequent to the superimposable loop 14 -24 are also shown.…”

Section: Resultsmentioning

confidence: 99%

“…2D). In the UDP-Glcbound OtsA structure, loop 14 -24 is partially disordered (14 -19), whereas the rest of the loop (20 -24) is 7-9 Å away from the substrate UDP-Glc (20), reminiscent of the comparable distance between GS loop [13][14][15][16][17][18][19][20] in the open apo-dmGS structure and the ADP-Glc (modeled by alignment of the EcGSb structure). In the presence of the substrate analogue UDP/imidazole and the acceptor Glc-6-P, the entire loop 14 -24 of OtsA becomes structured and moves to a position adjacent to the UDP molecule.…”

Section: Comparison Of the Open Adp-bound Atgs And The Closed Adp/glumentioning

confidence: 99%

The Crystal Structures of the Open and Catalytically Competent Closed Conformation of Escherichia coli Glycogen Synthase

Sheng¹,

Jia²,

Yep

et al. 2009

Journal of Biological Chemistry

129

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Escherichia coli glycogen synthase (EcGS, EC 2.4.1.21) is a retaining glycosyltransferase (GT) that transfers glucose from adenosine diphosphate glucose to a glucan chain acceptor with retention of configuration at the anomeric carbon. EcGS belongs to the GT-B structural superfamily. Here we report several EcGS x-ray structures that together shed considerable light on the structure and function of these enzymes. The structure of the wild-type enzyme bound to ADP and glucose revealed a 15.2°o verall domain-domain closure and provided for the first time the structure of the catalytically active, closed conformation of a glycogen synthase. The main chain carbonyl group of His-161, Arg-300, and Lys-305 are suggested by the structure to act as critical catalytic residues in the transglycosylation. Glu-377, previously thought to be catalytic is found on the ␣-face of the glucose and plays an electrostatic role in the active site and as a glucose ring locator. This is also consistent with the structure of the EcGS(E377A)-ADP-HEPPSO complex where the glucose moiety is either absent or disordered in the active site.

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“…In this context, we selected glycosyl fluorides as the donor, 10 which have been extensively studied by Jencks as models of substrates involved in the hydrolysis of glycosidic bonds (Scheme 1a). 11 More precisely, Jencks showed that α- d -glucosyl fluoride ( 1a ) reacts in an aqueous solution of sodium azide and acetate salts to produce the corresponding β-anomers 2a-b , overcoming the formation of d -glucose. However, the aqueous solvolysis of glycosyl fluorides in the presence of different alcohols as potential nucleophiles revealed a preference for reaction with water.…”

Section: Introductionmentioning

confidence: 99%

Aqueous Glycosylation of Unprotected Sucrose Employing Glycosyl Fluorides in the Presence of Calcium Ion and Trimethylamine

et al. 2016

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We report a synthetic glycosylation reaction between sucrosyl acceptors and glycosyl fluoride donors to yield the derived trisaccharides. This reaction proceeds at room temperature in an aqueous solvent mixture. Calcium salts and a tertiary amine base promote the reaction with high site-selectivity for either the 3′-position or 1′-position of the fructofuranoside unit. Because non-enzymatic aqueous oligosaccharide syntheses are underdeveloped, mechanistic studies were carried out in order to identify the origin of the selectivity, which we hypothesized was related to the structure of hydroxyl group array in sucrose. The solution conformation of various mono-deoxysucrose analogs revealed the cooperative nature of the hydroxyl group in mediating both this aqueous glycosyl bond-forming reaction and the site-selectivity at the same time.

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General-acid and general-base catalysis of the cleavage of .alpha.-D-glucopyranosyl fluoride

Cited by 69 publications

References 4 publications

Alkaline Phosphatase Mono- and Diesterase Reactions: Comparative Transition State Analysis

Alkaline Phosphatase Mono- and Diesterase Reactions: Comparative Transition State Analysis

The Crystal Structures of the Open and Catalytically Competent Closed Conformation of Escherichia coli Glycogen Synthase

Aqueous Glycosylation of Unprotected Sucrose Employing Glycosyl Fluorides in the Presence of Calcium Ion and Trimethylamine

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