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Reaction mechanism of the binuclear zinc enzyme glyoxalase II : A theoretical study

Chen, Shilu (author)
KTH,Teoretisk kemi
Fang, Wei-Hai (author)
Beijing Normal Univ, Coll Chem
Himo, Fahmi (author)
KTH,Teoretisk kemi
 (creator_code:org_t)
Elsevier BV, 2009
2009
English.
In: Journal of Inorganic Biochemistry. - : Elsevier BV. - 0162-0134 .- 1873-3344. ; 103:2, s. 274-281
  • Journal article (peer-reviewed)
Abstract Subject headings
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  • The glyoxalase system catalyzes the conversion of toxic methylglyoxal to nontoxic d-lactic acid using glutathione (GSH) as a coenzyme. Glyoxalase II (GlxII) is a binuclear Zn enzyme that catalyzes the second step of this conversion, namely the hydrolysis of S-d-lactoylglutathione, which is the product of the Glyoxalase I (GlxI) reaction. In this paper we use density functional theory method to investigate the reaction mechanism of GlxII. A model of the active site is constructed on the basis of the X-ray crystal structure of the native enzyme. Stationary points along the reaction pathway are optimized and the potential energy surface for the reaction is calculated. The calculations give strong support to the previously proposed mechanism. It is found that the bridging hydroxide is capable of performing nucleophilic attack at the substrate carbonyl to form a tetrahedral intermediate. This step is followed by a proton transfer from the bridging oxygen to Asp58 and finally C–S bond cleavage. The roles of the two zinc ions in the reaction mechanism are analyzed. Zn2 is found to stabilize the charge of tetrahedral intermediate thereby lowering the barrier for the nucleophilic attack, while Zn1 stabilizes the charge of the thiolate product, thereby facilitating the C–S bond cleavage. Finally, the energies involved in the product release and active-site regeneration are estimated and a new possible mechanism is suggested.

Subject headings

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)
NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Keyword

BETA-LACTAMASE; CRYSTAL-STRUCTURE; BACTERIAL PHOSPHOTRIESTERASE; BACTEROIDES-FRAGILIS; CATALYTIC MECHANISM; IN-VITRO; DENSITY; BINDING; METHYLGLYOXAL; HYDROLYSIS
Biochemistry
Biokemi

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Chen, Shilu
Fang, Wei-Hai
Himo, Fahmi
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NATURAL SCIENCES
NATURAL SCIENCES
and Biological Scien ...
and Biochemistry and ...
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Journal of Inorg ...
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Royal Institute of Technology

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