Natural product juglone targets three key enzymes from Helicobacter pylori: inhibition assay with crystal structure characterization

Yunhua Kong,Liang Zhang,Zheng-yi Yang,Cong Han,Li-Hong Hu,Hualiang Jiang,Xu Shen

Published 2008 in Acta Pharmacologica Sinica

ABSTRACT

AbstractAim:To investigate the inhibition features of the natural product juglone (5-hydroxy-1,4-naphthoquinone) against the three key enzymes from Helicobacter pylori (cystathionine γ-synthase [HpCGS], malonyl-CoA:acyl carrier protein transacylase [HpFabD], and β-hydroxyacyl-ACP dehydratase [HpFabZ]).Methods:An enzyme inhibition assay against HpCGS was carried out by using a continuous coupled spectrophotometric assay approach. The inhibition assay of HpFabD was performed based on the α-ketoglutarate dehydrogenase-coupled system, while the inhibition assay for HpFabZ was monitored by detecting the decrease in absorbance at 260 nm with crotonoyl-CoA conversion to β-hydroxybutyryl-CoA. The juglone/FabZ complex crystal was obtained by soaking juglone into the HpFabZ crystal, and the X-ray crystal structure of the complex was analyzed by molecular replacement approach.Results:Juglone was shown to potently inhibit HpCGS, HpFabD, and HpFabZ with the half maximal inhibitory concentration IC50 values of 7.0±0.7, 20±1, and 30±4 μmol/L, respectively. An inhibition-type study indicated that juglone was a non-competitive inhibitor of HpCGS against O-succinyl-L-homoserine (Ki=αKi=24 μmol/L), an uncompetitive inhibitor of HpFabD against malonyl-CoA (αKi=7.4 μmol/L), and a competitive inhibitor of HpFabZ against crotonoyl-CoA (Ki=6.8 μmol/L). Moreover, the crystal structure of the HpFabZ/juglone complex further revealed the essential binding pattern of juglone against HpFabZ at the atomic level.Conclusion:HpCGS, HpFabD, and HpFabZ are potential targets of juglone.

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