Abstract
The heme aa3 type cytochrome oxidase from Paracoccus denitrificans incorporated into vesicles with phospholipid reacts during turnover much as the oxidase from mitochondria does. The spectrophotometric changes observed at various wavelengths are closely similar, and the rate is about one-half of that for beef heart oxidase under the same conditions. The rate of appearance of oxidized cytochrome c on initiation of the reaction is also similar and depends on the previous treatment of the oxidase as described by Antonini, E., Brunori, M., Colosimo, A., Greenwood, C. and Wilson, M. T. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 3128-3132. In terms of their model the resting Paracoccus enzyme is converted to the pulsed form during turnover. The effect is observed with both cytochrome c and hexamine ruthenium as reductants. With the latter a 60-fold increase in rate is observed.
Highlights
Paracoccus enzyme having onlytwo subunits rather than the obtained for the two phases by repeating the experimenwt ith seven or more of the mitochondrial enzyme, immu- light of differentwavelengths are of thesameorder.It is nological cross-reactions between Paracoccus and mitochon- reasonableto suggest thatthecomponentsarepresent in drial oxidase subunit I1 have been reported [1]
The experiments reported here show that the Paracoccus and mitochondrialenzymes are similar in the series of reductive reactions involved in turnover with both cytochrome c and hexamine ruthenium as reducingagents
An analogous pulsing effect occurswith hexamine ruthenium, and it too is common to both enzymes
Summary
From the Section of Biochemistry, Cellulur and Molecular Biology, Cornell UniLvysity, Ithacu, N e w Yorh 14853. The rate of appearance of oxidized cytochrome c on initiation of the reaction is similar and depends on the previous treatment of the oxidase as described by Antonini, E., Enzyme activity was measured at room temperature(24 f 1 “C)with aClark-type oxygen electrodewith a Teflonmembrane(Yellow Springs Instruments, Yellow Springs, OH) in a medium containing 0.1 M KP,, pH 7.0, 30 p~ horse heart cytochrome c (Sigma type VI), 1 0 mM potassiumascorbate,and 100 PM N,N,N’,N’-tetramethyl-~phenylenediamine. The effect is observed with both cytochrome c and hexamine ruthenium as reductants. With the latter a 60-fold increase in rate is observed. Oxygen concentrations were calculated from the dataof Lange [15]
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