title: Interaction of ebselen with glutathione S-transferase and papain in vitro.
abstract: The interaction of ebselen(2-phenyl-1,2-benzisoselenazol-3(2H)-one) with rat liver cytosolic glutathione S-transferases (GSTs) and the plant cysteine protease, papain, was studied as cysteine residues are important for the activity of these enzymes. The capacity of GST 1-2 and 3-4 for ebselen binding is similar (1.5 mol ebselen/mol GST isozyme), while GST 2-2 and GST 7-7 bind 0.3 and more than 2.0 mol ebselen/mol GST isozyme, respectively. Ebselen does not bind to N-ethylmaleimide-treated GST, and its binding to GST is prevented by 5 mM thiols. Ebselen irreversibly inactivates the different GST isozymes with a second order rate constant ranging from 20 to 2250 M-1 sec-1 for the different subunits. GST inhibition by ebselen is partially restored by 5 mM thiols. Ebselen binds to untreated papain and to cysteine-treated papain at a ratio of about 0.1 and 0.75 mol ebselen/mol papain, respectively. Ebselen does not bind to N-ethylmaleimide-treated papain, and its binding to papain is interfered with by added thiols. Papain is inactivated by ebselen with a second order rate constant of 1800 M-1 sec-1 in the absence of thiols. However, in the presence of GSH, 2-mercaptoethanol or sodium borohydride, ebselen exerts an activating effect on papain. The binding of ebselen by a seleno-sulfide bond to cysteine residues of GSTs and papain leads to their inactivation.
authors.affiliation: Institut für Physiologische Chemie I, Heinrich-Heine-Universität Düsseldorf, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Nikawa
authors.forename: G
authors.initials: G
authors.lastname: Schuch
authors.forename: G
authors.initials: G
authors.lastname: Wagner
authors.forename: H
authors.initials: H
authors.lastname: Sies
mesh_terms: D000818:Animals; D001393:Azoles / Q000378:metabolism* / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D054833:Isoindoles; D008297:Male; D016566:Organoselenium Compounds / Q000378:metabolism* / Q000494:pharmacology; D010206:Papain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013056:Spectrophotometry, Ultraviolet; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D001393:Azoles; D007527:Isoenzymes; D054833:Isoindoles; D016566:Organoselenium Compounds; D013438:Sulfhydryl Compounds; C042986:ebselen; D005982:Glutathione Transferase; D010206:Papain; D005033:Ethylmaleimide