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Occurrence of heme O in photoheterotrophically growing, semi‐anaerobic cyanobacterium Synechocystis sp. PCC6803
Author(s) -
Peschek Günter A.,
Wastyn Marnik,
Fromwald Susanne,
Mayer Bernhard
Publication year - 1995
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(95)00821-p
Subject(s) - heme , heme a , chemistry , cytochrome , synechocystis , oxidase test , cytochrome c oxidase , hemeprotein , oxygen , biochemistry , cyanobacteria , enzyme , biology , organic chemistry , bacteria , mutant , gene , genetics
Extraction and identification of the non‐covalently bound heme groups from crude membrane preparations of photoheterotrophically grown Synechocystis sp. PCC 6803 by reversed phase high performance liquid chromatography and optical spectrophotometry led to the detection of heme O in addition to hemes B and A which latter was to be expected from the known presence of aa 3 ‐type cytochrome oxidase in cyanobacteria. In fully aerated cells (245 μM dissolved O 2 in the medium) besides heme B only heme A was found while in low‐oxygen cells (<10 μ M dissolved O 2 ) heme O was present at a concentration even higher than that of heme A. Given the possible role of heme O as a biosynthetic intermediate between heme B and heme A, together with generally much higher K m values of 5–50 μM O 2 for oxygenase as compared to K m values of 40–70 nM O 2 for typical cytochrome‐ c oxidase, our findings may permit the conclusion that the conversion of heme O to heme A is an obligately oxygen‐requiring process catalyzed by some oxygenase directly introducing oxygen from O 2 into the 8‐methyl group of heme O. At the same time thus the occurrence of heme O (cytochrome o ) in cyanobacteria does of course not imply the existence of an ‘alternative oxidase’ since according to the well‐known ‘promiscuity of heme groups’ both hemes O and A are likely to combine with one and the same apoprotein.