ISSN:
1573-6881
Keywords:
Oxygen intermediates
;
electron transfer
;
flow flash
;
Bacillus PS3
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract The time course of absorbance changes following flash photolysis of the fully-reduced carboxycytochrome oxidase fromBacillus PS3 in the presence of O2 has been followed at 445, 550, 605, and 830 nm, and the results have been compared with the corresponding changes in bovine cytochrome oxidase. The PS3 enzyme has a covalently bound cytochromec subunit and the fully-reduced species therefore accommodates five electrons instead of four as in the bovine enzyme. In the bovine enzyme, following CO dissociation, four phases were observed with time constants of about 10 Μs, 30 Μs, 100 Μs, and 1 ms at 445 nm. The initial, 10-Μs absorbance change at 445 nm is similar in the two enzymes. The subsequent phases involving hemea and CuA are not seen in the PS3 enzyme at 445 nm, because these redox centers are re-reduced by the covalently bound cytochromec, as indicated by absorbance changes at 550 nm. A reaction scheme consistent with the experimental observations is presented. In addition, internal electron-transfer reactions in the absence of O2 were studied following flash-induced CO dissociation from the mixed-valence enzyme. Comparisons of the CO recombination rates in the mixed-valence and fully-reduced oxidases indicate that more electrons were transferred from hemea 3 toa in PS3 oxidase compared to the bovine enzyme.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02110439
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