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Structural basis for 18-β-glycyrrhetinic acid as a novel non-GSH analog glyoxalase I inhibitor.

Zhang H, Huang Q, Zhai J, Zhao YN, Zhang LP, Chen YY, Zhang RW, Li Q, Hu XP - Acta Pharmacol. Sin. (2015)

Bottom Line: The crystal structure of the mGLOI-GA complex showed that the carboxyl group of GA mimicked the γ-glutamyl residue of GSH by hydrogen bonding to the glutamyl sites (residues Arg38B, Asn104B and Arg123A) in the GSH binding site of mGLOI.The extensive van der Waals interactions between GA and the surrounding residues also contributed greatly to the binding of GA and mGLOI.This work demonstrates a carboxyl group to be an important functional feature of non-GSH analog GLOI inhibitors.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmaceutical Sciences & Centre for Cellular and Structural Biology of Sun Yat-sen University, Guangzhou 510006, China.

ABSTRACT

Aim: Glyoxalase I (GLOI), a glutathione (GSH)-dependent enzyme, is overexpressed in tumor cells and related to multi-drug resistance in chemotherapy, making GLOI inhibitors as potential anti-tumor agents. But the most studied GSH analogs exhibit poor pharmacokinetic properties. The aim of this study was to discover novel non-GSH analog GLOI inhibitors and analyze their binding mechanisms.

Methods: Mouse GLOI (mGLOI) was expressed in BL21 (DE3) pLysS after induction with isopropyl-β-D-1-thiogalactopyranoside and purified using AKTA FPLC system. An in vitro mGLOI enzyme assay was used to screen a small pool of compounds containing carboxyl groups. Crystal structure of the mGLOI-inhibitor complex was determined at 2.3 Å resolution. Molecular docking study was performed using Discovery Studio 2.5 software package.

Results: A natural compound 18-β-glycyrrhetinic acid (GA) and its derivative carbenoxolone were identified as potent competitive non-GSH analog mGLOI inhibitors with Ki values of 0.29 μmol/L and 0.93 μmol/L, respectively. Four pentacyclic triterpenes (ursolic acid, oleanolic acid, betulic acid and tripterine) showed weak activities (mGLOI inhibition ratio <25% at 10 μmol/L) and other three (maslinic acid, corosolic acid and madecassic acid) were inactive. The crystal structure of the mGLOI-GA complex showed that the carboxyl group of GA mimicked the γ-glutamyl residue of GSH by hydrogen bonding to the glutamyl sites (residues Arg38B, Asn104B and Arg123A) in the GSH binding site of mGLOI. The extensive van der Waals interactions between GA and the surrounding residues also contributed greatly to the binding of GA and mGLOI.

Conclusion: This work demonstrates a carboxyl group to be an important functional feature of non-GSH analog GLOI inhibitors.

No MeSH data available.


Related in: MedlinePlus

Structure of GA binding to mGLOI. 2Fo-Fc electron density map of GA contoured at 1.0 sigma. The protein and ligand surfaces are depicted as a transparent light blue and yellow cutaway. Key residues and ligands are shown as magenta and yellow stick models, respectively. Hydrogen bonds are shown as red dashed lines.
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fig2: Structure of GA binding to mGLOI. 2Fo-Fc electron density map of GA contoured at 1.0 sigma. The protein and ligand surfaces are depicted as a transparent light blue and yellow cutaway. Key residues and ligands are shown as magenta and yellow stick models, respectively. Hydrogen bonds are shown as red dashed lines.

Mentions: A schematic presentation of the GA-occupied active site derived from the mGLOI-GA complex crystal structure revealed that GA did not coordinate with Zn2+; instead, it nestled in the GSH binding subpocket with its hydroxyl group pointing toward the glutamyl site and established a hydrogen-bonding network with mArg38B (-O2•••Nɛ, 2.4 Å -O3•••HN, 3.2 Å), mAsn104B (-O2•••HN, 3.4 Å) and mArg123A (-O2•••HN, 3.2 Å -O2•••HN, 3.4 Å) (Figure 2). The full occupation of GA in the GSH binding subpocket also resulted in extensive van der Waals interactions with the surrounding residues mMet36B, mMet66B, mPhe68B, mThr102B, mAsn104B, mVal150A, mLys151A, mPhe163A and mTrp171A, in addition to at least three nonpolar/polar and ten nonpolar/nonpolar contacts with distances shorter than 4 Å (Figure 2 and Table 2).


Structural basis for 18-β-glycyrrhetinic acid as a novel non-GSH analog glyoxalase I inhibitor.

Zhang H, Huang Q, Zhai J, Zhao YN, Zhang LP, Chen YY, Zhang RW, Li Q, Hu XP - Acta Pharmacol. Sin. (2015)

Structure of GA binding to mGLOI. 2Fo-Fc electron density map of GA contoured at 1.0 sigma. The protein and ligand surfaces are depicted as a transparent light blue and yellow cutaway. Key residues and ligands are shown as magenta and yellow stick models, respectively. Hydrogen bonds are shown as red dashed lines.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4561975&req=5

fig2: Structure of GA binding to mGLOI. 2Fo-Fc electron density map of GA contoured at 1.0 sigma. The protein and ligand surfaces are depicted as a transparent light blue and yellow cutaway. Key residues and ligands are shown as magenta and yellow stick models, respectively. Hydrogen bonds are shown as red dashed lines.
Mentions: A schematic presentation of the GA-occupied active site derived from the mGLOI-GA complex crystal structure revealed that GA did not coordinate with Zn2+; instead, it nestled in the GSH binding subpocket with its hydroxyl group pointing toward the glutamyl site and established a hydrogen-bonding network with mArg38B (-O2•••Nɛ, 2.4 Å -O3•••HN, 3.2 Å), mAsn104B (-O2•••HN, 3.4 Å) and mArg123A (-O2•••HN, 3.2 Å -O2•••HN, 3.4 Å) (Figure 2). The full occupation of GA in the GSH binding subpocket also resulted in extensive van der Waals interactions with the surrounding residues mMet36B, mMet66B, mPhe68B, mThr102B, mAsn104B, mVal150A, mLys151A, mPhe163A and mTrp171A, in addition to at least three nonpolar/polar and ten nonpolar/nonpolar contacts with distances shorter than 4 Å (Figure 2 and Table 2).

Bottom Line: The crystal structure of the mGLOI-GA complex showed that the carboxyl group of GA mimicked the γ-glutamyl residue of GSH by hydrogen bonding to the glutamyl sites (residues Arg38B, Asn104B and Arg123A) in the GSH binding site of mGLOI.The extensive van der Waals interactions between GA and the surrounding residues also contributed greatly to the binding of GA and mGLOI.This work demonstrates a carboxyl group to be an important functional feature of non-GSH analog GLOI inhibitors.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmaceutical Sciences & Centre for Cellular and Structural Biology of Sun Yat-sen University, Guangzhou 510006, China.

ABSTRACT

Aim: Glyoxalase I (GLOI), a glutathione (GSH)-dependent enzyme, is overexpressed in tumor cells and related to multi-drug resistance in chemotherapy, making GLOI inhibitors as potential anti-tumor agents. But the most studied GSH analogs exhibit poor pharmacokinetic properties. The aim of this study was to discover novel non-GSH analog GLOI inhibitors and analyze their binding mechanisms.

Methods: Mouse GLOI (mGLOI) was expressed in BL21 (DE3) pLysS after induction with isopropyl-β-D-1-thiogalactopyranoside and purified using AKTA FPLC system. An in vitro mGLOI enzyme assay was used to screen a small pool of compounds containing carboxyl groups. Crystal structure of the mGLOI-inhibitor complex was determined at 2.3 Å resolution. Molecular docking study was performed using Discovery Studio 2.5 software package.

Results: A natural compound 18-β-glycyrrhetinic acid (GA) and its derivative carbenoxolone were identified as potent competitive non-GSH analog mGLOI inhibitors with Ki values of 0.29 μmol/L and 0.93 μmol/L, respectively. Four pentacyclic triterpenes (ursolic acid, oleanolic acid, betulic acid and tripterine) showed weak activities (mGLOI inhibition ratio <25% at 10 μmol/L) and other three (maslinic acid, corosolic acid and madecassic acid) were inactive. The crystal structure of the mGLOI-GA complex showed that the carboxyl group of GA mimicked the γ-glutamyl residue of GSH by hydrogen bonding to the glutamyl sites (residues Arg38B, Asn104B and Arg123A) in the GSH binding site of mGLOI. The extensive van der Waals interactions between GA and the surrounding residues also contributed greatly to the binding of GA and mGLOI.

Conclusion: This work demonstrates a carboxyl group to be an important functional feature of non-GSH analog GLOI inhibitors.

No MeSH data available.


Related in: MedlinePlus