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. 2014 Jan 8;9(1):e85544. doi: 10.1371/journal.pone.0085544

Figure 4. Reversible generation and metabolic consequences of FeII-NO CBS.

Figure 4

(A) Reduction of FeIII-CBS (10 µM) in 0.1 M HEPES buffer, pH 7.4, (-••-) with dithionite (3 mM) yields FeII-CBS (–). The latter reacts with 10 mM nitrite to give FeII-NO CBS (….). The NO ligand is exchanged for CO upon incubation of the reaction mixture for 10–15 min with CO (––). (B) Effect of NO binding to FeII-CBS on H2S production was measured in 0.1 M HEPES buffer, pH 7.4 using cysteine (10 mM) and homocysteine (10 mM) as substrates. H2S generation was assesed using the lead sulfide precipitation assay. (C) Predicted metabolic consequences of FeII-NO CBS formation. Inhibition of CBS by its nitrite reductase activity is predicted to decrease CBS-dependent H2S formation while increasing cystathionase (CSE)-dependent H2S formation due to homocysteine accumulation. The concentration of the antioxidant glutathione (GSH), is also predicted to decrease.