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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

The Dixon plots and chemical structures of GA (A) and carbenoxolone (B). Data are the mean±SD (error bars) of n=3 experiments.
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fig1: The Dixon plots and chemical structures of GA (A) and carbenoxolone (B). Data are the mean±SD (error bars) of n=3 experiments.

Mentions: To search for GLOI inhibitors with a carboxyl group feature, we screened a small pool of compounds containing carboxyl groups using an in vitro assay. Among this pool, GA was found to be a potent competitive mGLOI inhibitor with a Ki of 0.29 μmol/L (Figure 1A), and its derivative carbenoxolone (a licensed drug) showed a slightly lower inhibitory activity with a Ki of 0.93 μmol/L (Figure 1B). Seven other natural pentacyclic triterpenes in this pool showed only slight mGLOI inhibitory activity (ursolic acid, oleanolic acid, betulic acid and tripterine with inhibition ratios <25% at a concentration of 10 μmol/L; Table 1) or no activity (maslinic acid, corosolic acid and madecassic acid; Table 1). Although a subsequent literature review indicated that GA had been identified as human GLOI inhibitor by Masayoshi et al in 198627, no further studies on the mechanism of inhibition or the structure-activity relationship were performed.


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)

The Dixon plots and chemical structures of GA (A) and carbenoxolone (B). Data are the mean±SD (error bars) of n=3 experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4561975&req=5

fig1: The Dixon plots and chemical structures of GA (A) and carbenoxolone (B). Data are the mean±SD (error bars) of n=3 experiments.
Mentions: To search for GLOI inhibitors with a carboxyl group feature, we screened a small pool of compounds containing carboxyl groups using an in vitro assay. Among this pool, GA was found to be a potent competitive mGLOI inhibitor with a Ki of 0.29 μmol/L (Figure 1A), and its derivative carbenoxolone (a licensed drug) showed a slightly lower inhibitory activity with a Ki of 0.93 μmol/L (Figure 1B). Seven other natural pentacyclic triterpenes in this pool showed only slight mGLOI inhibitory activity (ursolic acid, oleanolic acid, betulic acid and tripterine with inhibition ratios <25% at a concentration of 10 μmol/L; Table 1) or no activity (maslinic acid, corosolic acid and madecassic acid; Table 1). Although a subsequent literature review indicated that GA had been identified as human GLOI inhibitor by Masayoshi et al in 198627, no further studies on the mechanism of inhibition or the structure-activity relationship were performed.

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