Higher Flexibility of Glu-172 Explains the Unusual Stereospecificity of Glyoxalase i
Jafari, Sonia ; Kazemi, Nadia ; Ryde, Ulf LU
and Irani, Mehdi
LU
(2018)
In Inorganic Chemistry
57(9).
p.4944-4958
- Abstract
Despite many studies during the latest two decades, the reason for the unusual stereospecificity of glyoxalase I (GlxI) is still unknown. This metalloenzyme converts both enantiomers of its natural substrate to only one enantiomer of its product. In addition, GlxI catalyzes reactions involving some substrate and product analogues with a stereospecificity similar to that of its natural substrate reaction. For example, the enzyme exchanges the pro-S, but not the pro-R, hydroxymethyl proton of glutathiohydroxyacetone (HOC-SG) with a deuterium from D2O. To find some clues to the unusual stereospecificity of GlxI, we have studied the stereospecific proton exchange of the hydroxymethyl proton of HOC-SG by this enzyme. We employed... (More)
Despite many studies during the latest two decades, the reason for the unusual stereospecificity of glyoxalase I (GlxI) is still unknown. This metalloenzyme converts both enantiomers of its natural substrate to only one enantiomer of its product. In addition, GlxI catalyzes reactions involving some substrate and product analogues with a stereospecificity similar to that of its natural substrate reaction. For example, the enzyme exchanges the pro-S, but not the pro-R, hydroxymethyl proton of glutathiohydroxyacetone (HOC-SG) with a deuterium from D2O. To find some clues to the unusual stereospecificity of GlxI, we have studied the stereospecific proton exchange of the hydroxymethyl proton of HOC-SG by this enzyme. We employed density functional theory and molecular dynamics (MD) simulations to study the proton exchange mechanism and origin of the stereospecificity. The results show that a rigid cluster model with the same flexibility for the two active-site glutamate residues cannot explain the unusual stereospecificity of GlxI. However, using a cluster model with full flexibility of Glu-172 or a larger model with the entire glutamates, extending the backbone into the neighboring residues, the results showed that there is no way for HOC-SG to exchange its protons if the alcoholic proton is directed toward Glu-99. However, if the hydroxymethyl proton instead is directed toward the more flexible Glu-172, we find a catalytic reaction mechanism for the exchange of the HS proton by a deuterium, in accordance with experimental findings. Thus, our results indicate that the special stereospecificity of GlxI is caused by the more flexible environment of Glu-172 in comparison to that of Glu-99. This higher flexibility of Glu-172 is also confirmed by MD simulations. We propose a reaction mechanism for the stereospecific proton exchange of the hydroxymethyl proton of HOC-SG by GlxI with an overall energy barrier of 15 kcal/mol.
(Less)
- author
- Jafari, Sonia
; Kazemi, Nadia
; Ryde, Ulf
LU
and Irani, Mehdi
LU
- organization
- publishing date
- 2018-05-07
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Inorganic Chemistry
- volume
- 57
- issue
- 9
- pages
- 15 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:85046681737
- pmid:29634252
- ISSN
- 0020-1669
- DOI
- 10.1021/acs.inorgchem.7b03215
- language
- English
- LU publication?
- yes
- id
- dced8c83-84e4-413b-950d-8d11c44a52d3
- date added to LUP
- 2018-05-24 13:03:36
- date last changed
- 2024-05-27 12:05:07
@article{dced8c83-84e4-413b-950d-8d11c44a52d3,
abstract = {{<p>Despite many studies during the latest two decades, the reason for the unusual stereospecificity of glyoxalase I (GlxI) is still unknown. This metalloenzyme converts both enantiomers of its natural substrate to only one enantiomer of its product. In addition, GlxI catalyzes reactions involving some substrate and product analogues with a stereospecificity similar to that of its natural substrate reaction. For example, the enzyme exchanges the pro-S, but not the pro-R, hydroxymethyl proton of glutathiohydroxyacetone (HOC-SG) with a deuterium from D<sub>2</sub>O. To find some clues to the unusual stereospecificity of GlxI, we have studied the stereospecific proton exchange of the hydroxymethyl proton of HOC-SG by this enzyme. We employed density functional theory and molecular dynamics (MD) simulations to study the proton exchange mechanism and origin of the stereospecificity. The results show that a rigid cluster model with the same flexibility for the two active-site glutamate residues cannot explain the unusual stereospecificity of GlxI. However, using a cluster model with full flexibility of Glu-172 or a larger model with the entire glutamates, extending the backbone into the neighboring residues, the results showed that there is no way for HOC-SG to exchange its protons if the alcoholic proton is directed toward Glu-99. However, if the hydroxymethyl proton instead is directed toward the more flexible Glu-172, we find a catalytic reaction mechanism for the exchange of the H<sub>S</sub> proton by a deuterium, in accordance with experimental findings. Thus, our results indicate that the special stereospecificity of GlxI is caused by the more flexible environment of Glu-172 in comparison to that of Glu-99. This higher flexibility of Glu-172 is also confirmed by MD simulations. We propose a reaction mechanism for the stereospecific proton exchange of the hydroxymethyl proton of HOC-SG by GlxI with an overall energy barrier of 15 kcal/mol.</p>}},
author = {{Jafari, Sonia and Kazemi, Nadia and Ryde, Ulf and Irani, Mehdi}},
issn = {{0020-1669}},
language = {{eng}},
month = {{05}},
number = {{9}},
pages = {{4944--4958}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Inorganic Chemistry}},
title = {{Higher Flexibility of Glu-172 Explains the Unusual Stereospecificity of Glyoxalase i}},
url = {{http://dx.doi.org/10.1021/acs.inorgchem.7b03215}},
doi = {{10.1021/acs.inorgchem.7b03215}},
volume = {{57}},
year = {{2018}},
}