title: Ca(2+)-sensitive reduction of 5,5'-dithiobis-(2-nitrobenzoic acid) by rat liver mitochondria.
abstract: Energized rat liver mitochondria in the presence of EGTA reduced linearly 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) at the rate of 7 nmol SH/min per mg protein within more than 1 hour at 20 degrees C. The Km for DTNB, 1.4 mM, was decreased by Mg2+ and spermine to 0.5 and 0.7 mM, respectively. The reaction was suppressed under conditions of decreasing mitochondrial content of NADPH, was blocked by 1,3-bis-(2-chloroethyl)-1-nitrosourea, the inhibitor of disulfide reductases, and was sensitive to external free Ca2+ in the micromolar range. After lysis of mitochondria the reduction of DTNB required the addition of NADPH and EGTA and was inhibited by 1 mM sodium arsenite. These observations suggest that the reduction of DTNB by mitochondria is catalyzed by Ca(2+)-sensitive thioredoxin reductase (EC 1.6.4.5).
authors.affiliation: Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Lenartowicz
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002330:Carmustine / Q000494:pharmacology; D004228:Dithionitrobenzoic Acid / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D013096:Spermine / Q000494:pharmacology
chemical_list: D013096:Spermine; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D009249:NADP; D004228:Dithionitrobenzoic Acid; D004492:Edetic Acid; D008274:Magnesium; D002118:Calcium; D002330:Carmustine