Avtor/Urednik		Bašica, Branka; Mihaljević, Ivan; Maraković, Nikola; Kovačević, Radmila; Smital, Tvrdko
Naslov		Molecular characterization of zebrafish Gstr1, the only member of teleost-specific glutathione S- transferase class
Tip		članek
Vol. in št.		, št. Vol. 208
Leto izdaje		2019
Obseg		str. 196-207
ISSN		0166-445X - Aquatic toxicology (Amsterdam, Netherlands)
Jezik		eng
Abstrakt		Glutathione S-transferases (GSTs) are multifunctional phase II detoxification enzymes with primary function of glutathione conjugation of various endogenous and exogenous compounds. Teleost-specific Gstr1 in zebrafish (Danio rerio) was previously shown to have high expression in toxicologically relevant tissues and high activity towards model substrates. The aim of this study was a detailed functional characterization of zebrafish Gstr1. Molecular docking analyses were used to get novel insight into structural characteristics of Gstr1 and elucidation of the mechanistic interactions with both GSH and various Gstr1 substrates or inhibitors. An initial screening inhibition assay performed using model fluorescence substrate monochlorobimane (MCB) revealed interactions of different endogenous compounds and environmentally relevant xenobiotics with zebrafish Gstr1. All interacting compounds were further analyzed to determine their inhibition type and Ki values. Our data revealed that pregnenolone, progesterone, testosterone, DHEAS and corticosterone competitively inhibited transformation of MCB by Gstr1 with the calculated Ki values in the range 14-26 [micro]M, implying that these hormones are physiological substrates of zebrafish Gstr1. Estrogens had no effect on Gstr1 activity. Taurochenodeoxycholate (TCDC) expressed lower inhibition potency toward Gstr1 with the Ki value of 33 [micro]M. Among tested xenobiotics tributyltin chloride and rifampicin non-enzymatically bound Gstr1 enzyme (the calculated Ki values are 0.26 [micro]M and 65 [micro]M, respectively) and inhibited its activity, showing that these compounds are reversible noncompetitive inhibitors of zebrafish Gstr1. Insecticide diazinon competitively inhibited Gstr1 activity with calculated Ki value of 27 [micro]M, while other Gstr1-interacting insecticides, chlorpyrifos-methyl (CPF-methyl) and malathion, showed allosteric activation-like effect. Among tested pharmaceuticals, tetracycline, erythromycin and methotrexate demonstrated competitive type of inhibition with the calculated Ki values of 17.5, 36.5 and 29 [micro]M, respectively. In summary, we suggest that zebrafish Gstr1 has an important role in steroidogenesis, metabolism and/or physiological actions of androgens, but not estrogens in fish. Finally, our results imply the role of Gstr1 in metabolism of xenobiotics and protection of fish against deleterious environmental contaminants such as organophosphate insecticides and pharmaceuticals.
Proste vsebinske oznake		endogenous compounds functional characterization interaction screening endogene spojine funkcionalna karakterizacija pregled interakcij