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Hydrogen sulphide as inhibitor and substrates for the cytochrome c-cytochrome c oxidase system /

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dc.contributor.author Kim, Jae-Kyoung. en_US
dc.date.accessioned 2009-09-23T15:49:53Z
dc.date.available 2009-09-23T15:49:53Z
dc.date.issued 1981-09-23T15:49:53Z
dc.identifier.uri http://hdl.handle.net/10464/2725
dc.description.abstract It has previously been recognized that the major biochemical toxicity induced by sulphide is due to an inhibition of cytochrome ~ oxidase. Inhibition of this enzyme occurs at 30°C and pH 7.4 with a Ki of approximately 0.2 ~M, and a kon of 104 M-1 s-l, under catalytic conditions. However, the equimo1ar mixture of sulphide and the enzyme shows identical catalytic behaviour to that of the native enzyme. This cannot readily be attributed to rapid dissociation of sulphide, as both spectroscopic and plot analysis indicate the koff value is low. The addition of stoichiometric sulphide to the resting oxidized enzyme gives rise to the appearance of a low-spin ferric-type spectrum not identical with that seen on the addition of excess sulphide to the enzyme aerobically. Sulphide added to the enzyme anaerobically gives rise to another low-spin, probably largely ferric, form which upon admission of oxygen is then converted into a 607 nm species closely resembling Compound C. The 607 nm form is probably the precursor of oxyferricytochrome aa3. The addition of successive a1iquots of Na2S solution to the enzyme induces initial uptake of approximately 3 moles of oxygen per mole of the enzyme. Thus, it is concluded that: 1. the initial product of sulphide-cytochrome c oxidase interaction is not an inhibited form of the enzyme, but the low-spin (oxyferri) ~3+~+ species; 2. a subsequent step in which sulphide reduces cytochrome ~ occurs; 3. the final inhibitory step, in which a further molecule of sulphide binds to the cytochrome ~ iron centre in the cytochrome ~2+~+ species, gives the cytochrome a2+~+-H2S form which is a half-reduced fully inhibited species;4. a 607 run form of the enzyme is produced which may be converted into a catalytically active low-spin (oxyferri) state; and therefore 5. liganded sulphide may be able to reduce the cytochrome 33 -Cu centre without securing the prior reduction of the cytochrome a_ haem group or the Cud centre associated with it. en_US
dc.language.iso eng en_US
dc.publisher Brock University en_US
dc.subject Hydrogen sulfide. en_US
dc.subject Cytochrome c. en_US
dc.subject Cytochrome oxidase. en_US
dc.subject Chemical inhibitors. en_US
dc.title Hydrogen sulphide as inhibitor and substrates for the cytochrome c-cytochrome c oxidase system / en_US
dc.type Electronic Thesis or Dissertation en_US
dc.degree.name M.Sc. Biological Sciences en_US
dc.degree.level Masters en_US
dc.contributor.department Department of Biological Sciences en_US
dc.degree.discipline Faculty of Mathematics and Science en_US


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