Characterisation of naturally occurring isothiocyanates as glutathione reductase inhibitors

Xia Li; Maowei Ni; Xiaoling Xu; Wei Chen

doi:10.1080/14756366.2020.1822828

Characterisation of naturally occurring isothiocyanates as glutathione reductase inhibitors

J Enzyme Inhib Med Chem. 2020 Dec;35(1):1773-1780. doi: 10.1080/14756366.2020.1822828.

Authors

Xia Li^{1

2

3}, Maowei Ni^{1

2

3}, Xiaoling Xu^{1

2

4}, Wei Chen^{1

2

3

5

6}

Affiliations

¹ Cancer Hospital of the University of Chinese Academy of Sciences (Zhejiang Cancer Hospital), Hangzhou, China.
² Institute of Cancer and Basic Medicine, Chinese Academy of Sciences, Hangzhou, China.
³ Zhejiang Cancer Research Institute, Cancer Hospital of the University of Chinese Academy of Sciences, Hangzhou, China.
⁴ Department of Medical Oncology, Cancer Hospital of the University of Chinese Academy of Sciences, Hangzhou, China.
⁵ Zhejiang Key Laboratory of Radiation Oncology, Cancer Hospital of the University of Chinese Academy of Sciences, Hangzhou, China.
⁶ Zhejiang Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine on Cancer, Hangzhou, China.

Abstract

Glutathione reductase (GR), an essential antioxidant enzyme against oxidative stress, has become an attractive drug target for the development of anticancer and antimalarial drugs. In this regard, we evaluated the naturally occurring isothiocyanates as promising GR inhibitors and elucidated the mechanism of action. It was found that benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC) inhibited yeast GR (yGR) and human GR (hGR) in a time- and concentration-dependent manner. The K_i and k_inact of BITC against yGR were determined to be 259.87 µM and 0.0266 min^-1, respectively. The GR inhibition occurred only in the presence of NADPH and persisted after extensive dialysis. The tandem mass spectrometric analysis revealed that Cys⁶¹ rather than Cys⁶⁶ at the active site of yGR was mono-benzyl thiocarbamoylated by BITC. Inhibition of intracellular GR by BITC and PEITC in cultured cancer cells was also observed. BITC and PEITC were evaluated as competitive and irreversible inhibitors of GR.

Keywords: Glutathione reductase; inhibitor; isothiocyanate; thiocarbamoylation.

MeSH terms

Dose-Response Relationship, Drug
Enzyme Inhibitors / chemical synthesis
Enzyme Inhibitors / chemistry
Enzyme Inhibitors / pharmacology*
Glutathione Reductase / antagonists & inhibitors*
Glutathione Reductase / metabolism
Humans
Isothiocyanates / chemical synthesis
Isothiocyanates / chemistry
Isothiocyanates / pharmacology*
Molecular Structure
Structure-Activity Relationship
Tumor Cells, Cultured

Substances

Enzyme Inhibitors
Isothiocyanates
Glutathione Reductase

Grants and funding

This work was supported by the International Cooperation Fund from Science Technology Department of Zhejiang Province (LGJ19H160001); National Natural Science Foundation of China (81903641&81802995); Zhejiang Provincial Natural Science Foundation of China (LQ18H160016); Medical Science and Technology Project of Zhejiang Province (2018268942).