The Acid/Base Catalyst in the Exoglucanase/Xylanase from Cellulomonas fimi Is Glutamic Acid 127: Evidence from Detailed Kinetic Studies of Mutants

Biochemistry ◽  
1994 ◽  
Vol 33 (20) ◽  
pp. 6371-6376 ◽  
Author(s):  
Alasdair M. MacLeod ◽  
Thisbe Lindhorst ◽  
Stephen G. Withers ◽  
R. Antony J. Warren
Keyword(s):  
Glutamic Acid ◽  
Kinetic Studies ◽  
Base Catalyst ◽  
Acid Base ◽  
Cellulomonas Fimi

scholarly journals Glutamic acid 160 is the acid-base catalyst of β-xylosidase fromBacillus stearothermophilusT-6: a family 39 glycoside hydrolase

FEBS Letters ◽  
2001 ◽  
Vol 495 (1-2) ◽  
pp. 115-119 ◽  
Author(s):  
Tsafrir Bravman ◽  
Adva Mechaly ◽  
Smadar Shulami ◽  
Valery Belakhov ◽  
Timor Baasov ◽  
...  
Keyword(s):  
Glutamic Acid ◽  
Glycoside Hydrolase ◽  
Base Catalyst ◽  
Acid Base

1998 Hoffmann La Roche Award Lecture Understanding and exploiting glycosidases

1999 ◽  
Vol 77 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Stephen G Withers
Keyword(s):  
Amino Acid ◽  
Glutamic Acid ◽  
Three Dimensional ◽  
Acid Catalyst ◽  
Direct Consequence ◽  
Crystallographic Analysis ◽  
Base Catalyst ◽  
Acid Base ◽  
Efficient Catalyst ◽  
Important Amino Acid

Glycosidases fall into two major mechanistic classes; those that hydrolyse the glycosidic bond with retention of anomeric configuration and those that do so with inversion. Retaining glycosidases employ a mechanism involving a covalent glycosyl-enzyme intermediate formed and hydrolysed with acid-base catalytic assistance via oxocarbenium ion-like transition states. This intermediate has been trapped in two distinct ways, either by modification of the substrate through fluorination, or of the enzyme through mutation of key residues. This allows the amino acid residue to which this sugar is attached to be identified through LC/MS-MS analysis of peptic digests. Three-dimensional structures of several of these glycosyl-enzyme complexes, along with those of Michaelis complexes, have been determined through X-ray crystallographic analysis, revealing the identities of important amino acid residues involved in catalysis, particularly the involvement of the catalytic nucleophile in strong hydrogen bonding to the sugar 2-hydroxyl. They have also revealed evidence of substantial substrate distortion upon binding. Insight into the function of the acid-base catalyst Glu172 in Bacillus circulans xylanase has been obtained through NMR titration of side chain 13C-labelled glutamic acid enzyme both free and in the 2-fluoroxylobiosyl-enzyme complex. The pKa of Glu172 is relatively high in the free enzyme, consistent with its role as an acid catalyst, but drops 2.5 units upon formation of the intermediate, consistent with its new role as a base catalyst. This "cycling" of the pKa is shown to be a direct consequence of the change in charge of the nucleophile, Glu78. Finally, an efficient catalyst for synthesis, but not hydrolysis, of glycosidic bonds has been generated by mutation of the glutamic acid catalytic nucleophile of a β-glucosidase to an alanine. When used with alpha-glucosyl fluoride as a glycosyl donor, along with a suitable acceptor, oligosaccharides up to five sugars in length have been made with yields of up to 90% on individual steps. These new enzymes have been named glycosynthases.Key words: enzymatic mechanism, glycoside hydrolysis, inhibitors

Cesium-modified hollow ZSM-5: efficient acid-base catalyst for side-chain alkylation of 2-picoline with formaldehyde

2021 ◽  
pp. 117983
Author(s):  
Zhe Hong ◽  
Guoqing Zhao ◽  
Chuanfang Xiong ◽  
Wenzhi Jia ◽  
Fangtang Huang ◽  
...  
Keyword(s):  
Side Chain ◽  
Base Catalyst ◽  
Acid Base

scholarly journals Thermodynamic and Kinetic Studies on Adsorption of Vanadium with Glutamic Acid

ACS Omega ◽  
2021 ◽  
Author(s):  
Hao Peng ◽  
Hongzhi Qiu ◽  
Caiqiong Wang ◽  
Binfang Yuan ◽  
Huisheng Huang ◽  
...  
Keyword(s):  
Glutamic Acid ◽  
Kinetic Studies

scholarly journals Trigger loop of RNA polymerase is a positional, not acid–base, catalyst for both transcription and proofreading

2017 ◽  
pp. 201702383 ◽  
Author(s):  
Tatiana V. Mishanina ◽  
Michael Z. Palo ◽  
Dhananjaya Nayak ◽  
Rachel A. Mooney ◽  
Robert Landick
Keyword(s):  
Rna Polymerase ◽  
Base Catalyst ◽  
Acid Base ◽  
Trigger Loop

scholarly journals Can an Alcohol Act As an Acid/Base Catalyst in Water Solution? An Experimental and Theoretical Study of Imidazole Catalysis of the Aqueous Morita–Baylis–Hillman Reaction

ACS Catalysis ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 1703-1714 ◽  
Author(s):  
Lluís Raich ◽  
Hugo Santos ◽  
Juliana C. Gomes ◽  
Manoel T. Rodrigues ◽  
Renan Galaverna ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Water Solution ◽  
Base Catalyst ◽  
Acid Base ◽  
Imidazole Catalysis

scholarly journals Kinetic Studies of the Interaction of Toluidine Blue with Poly-(αL-glutamic acid) by Means of Stopped-Flow Method

1978 ◽  
Vol 10 (2) ◽  
pp. 153-159 ◽  
Author(s):  
Hidetoshi Ushio ◽  
Hiroshi Uchimura ◽  
Yoshikuni Tsuji ◽  
Takayuki Sano ◽  
Tatsuya Yasunaga
Keyword(s):  
Glutamic Acid ◽  
Toluidine Blue ◽  
Kinetic Studies ◽  
Stopped Flow ◽  
Flow Method

scholarly journals pKa Modulation of the Acid/Base Catalyst within GH32 and GH68: A Role in Substrate/Inhibitor Specificity?

PLoS ONE ◽  
2012 ◽  
Vol 7 (5) ◽  
pp. e37453 ◽  
Author(s):  
Shuguang Yuan ◽  
Katrien Le Roy ◽  
Tom Venken ◽  
Willem Lammens ◽  
Wim Van den Ende ◽  
...  
Keyword(s):  
Base Catalyst ◽  
Acid Base ◽  
Inhibitor Specificity ◽  
Substrate Inhibitor
Sign in / Sign up

Export Citation Format

Share Document