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Abstract
SUMMARY: Glutathione reductase was purified to homogeneity from the unicellular alga Chlamydomonas reinhardtii. The enzyme was a monomer with a molecular mass of 54-56 kDa as judged by gel filtration and SDS-PAGE. The activity was maximal at pH 8.2 and 49 °C. The enzyme was specific for NADPH, but not for NADH. The reverse reaction with NAD(P)+ and GSH (glutathione, reduced form) was not observed in the pH range 4.8-8.2. K m values for NADPH and GSSG (glutathione, oxidized form) were 10.6 μ;m and 54.1 μ;M, respectively. Thiol inhibitors and metal ions such as Hg2+ and Cu2+ markedly inhibited the enzyme activity. Activity was lost when the apoenzyme was prepared by dialysis, but was restored to 40% of the original activity by the addition of 50 μ;M-FAD. The enzyme reaction proceeded via a branching mechanism. Upon immunoprecipitation, glutathione reductase activity of C. reinhardtii was inhibited 50% and 90% by antibodies generated against spinach and Euglena glutathione reductases, respectively. Both antibodies cross-reacted with C. reinhardtii glutathione reductase in an immunoblot analysis.
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