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ELECTRON-TRANSFER FROM PHANEROCHAETE-CHRYSOSPORIUM CELLOBIOSE OXIDASE TO EQUINE CYTOCHROME-C AND PSEUDOMONAS-AERUGINOSA CYTOCHROME C-551
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THE OXYGEN REACTIVE SPECIES OF CYTOCHROME-C-OXIDASE - AN ALTERNATIVE VIEW
No full textIn a recent review article Babcok and Wikstrom (Nature, 1992, 356, 301-309) proposed that the species of cytochrome-c-oxidase which binds molecular oxygen during turnover is the so-called mixed valence enzyme, in which the binuclear center cytochrome a3-Cu(B) is reduced, while the cytochrome a/Cu(A) sites are oxidized. This proposal is based on earlier work (Morgan and Wikstrom, Biochemistry 1991, 30, 948-958) in which it was found that the steady-state reduction levels of cytochrome c and cytochrome a in respiring rat liver mitochondria (sustained by ascorbate and TMPD) are quite different, the latter being much more oxidized than the former; evaluation of the steady-state reduction levels demanded a large correction due to the optical contribution of oxidized TMPD+ which overlaps with the cytochromes. We report below that application of transient spectroscopy and SVD analysis to respiring rat heart myocytes, under conditions in which the contribution of TMPD+ is very small or absent, allows to show that the steady-state reduction levels of cytochrome c and cytochrome a are comparable at all times accessible to measurement in the rapid-scanning stopped-flow spectrophotometer. Our conclusion, in agreement with previous results, is that mixed valence cytochrome-c-oxidase as defined above is not the prevailing oxygen binding species of cytochrome-c-oxidase, unless electron donation to cytochrome c becomes rate limitin
THE REACTIONS BETWEEN THE CARBON-MONOXIDE COMPLEX OF CYTOCHROME-C OXIDASE AND OXYGEN - AN INVESTIGATION OF ELECTRON-TRANSFER BETWEEN THE FUNCTIONAL UNITS OF CYTOCHROME-C OXIDASE
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RECONSTITUTION OF MONOMERIC CYTOCHROME-C-OXIDASE INTO PHOSPHOLIPID-VESICLES YIELDS FUNCTIONALLY INTERACTING CYTOCHROME-AA3 UNITS
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