Interaction of Cu,Zn superoxide dismutase with hydrogen sulfide.
Addition of HS- enhanced the O(2-)-scavenging activity of bovine erythrocyte Cu,Zn superoxide dismutase (EC 1.15.1.1) by about twofold. The positive effect was measured using a diverse selection of SOD activity assays, and cannot be an artifact restricted to any single technique. Km values for HS- varied in different assay techniques, but we estimate Km approximately 80 microM HS-. In contrast to HS-, other small molecules tested with SOD either had little effect or were inhibitory. Consumption of HS- and O2- occurred in nearly 1:1 mole ratio. The products were H2O2 and sulfane sulfur, such as either elemental sulfur or polysulfide. Binding of HS- to the enzyme was rapid, with k > 10(7) M-1 s-1. The resulting complex exhibited a Cu-to-S charge-transfer absorbance band at 345 nm and an altered Cu(II) EPR spectrum. Taken together, these observations suggest that HS- binds at the catalytic Cu center of SOD and can be a genuine substrate of the enzyme.
Searcy
D G
DG
Department of Biology, University of Massachusetts, Amherst 01003, USA.
Whitehead
J P
JP
Maroney
M J
MJ
D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000032:analysis; D004578:Electron Spin Resonance Spectroscopy; D004912:Erythrocytes / Q000201:enzymology*; D006862:Hydrogen Sulfide / Q000378:metabolism*; D007700:Kinetics; D008962:Models, Theoretical; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013053:Spectrophotometry; D013482:Superoxide Dismutase / Q000097:blood / Q000737:chemistry / Q000378:metabolism*
D003574:Cytochrome c Group; D013482:Superoxide Dismutase; D006862:Hydrogen Sulfide