| 1575728 |
Lenartowicz E: Ca (2+)-sensitive reduction of 5,5'-dithiobis-(2-nitrobenzoic acid) by rat liver mitochondria. Biochem Biophys Res Commun. 1992 Apr 30;184(2):1088-93.
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). |
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