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Two K m values for cytochrome c of aa 3 ‐type two‐subunit cytochrome c oxidase from Nitrobacter agilis
Author(s) -
Fukumori Yoshihiro,
Yamanaka Tateo
Publication year - 1984
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(84)81332-0
Subject(s) - cytochrome c oxidase , cytochrome c , electron transport complex iv , cytochrome , protein subunit , oxidase test , chemistry , biochemistry , cytochrome b , enzyme , biology , mitochondrion , mitochondrial dna , gene
Oxidation of ferrocytochrome c by aa 3 ‐type two‐subunit cytochrome c oxidase from Nitrobacter agilis was measured polarographically and the results obtained were analyzed by means of Eadie‐Hofstee plots. Two apparent K m values of ∼3.0 × 10 −8 and 2.0 × 10 −6 M were obtained for horse cytochrome c in 25 mM phosphate buffer, pH 6.5. Also when N. agilis ferrocytochrome c was oxidized by the enzyme in 25 mM phosphate buffer (pH 6.5), two apparent K m values of ∼2.0 × 10 −8 and 4.0 × 10 −6 M were obtained although the break point in the Eadie‐Hofstee plot was as clear as in the case of horse cytochrome c . The results show that two reactive sites for cytochrome c also occur in the bacterial cytochrome c oxidase composed of two subunits and will give further support to the idea that only the larger two subunits of eukaryotic cytochrome c oxidase are responsible for oxidation of ferrocytochrome c .