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Characterization of extracellular oxygen consumption by the green alga Selenastrum minutum
Author(s) -
Weger Harold G.,
Lynnes Jaret A.,
Torkelson Joel D.
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1996.tb00213.x
Subject(s) - salicylhydroxamic acid , peroxidase , cyanide , biochemistry , cytochrome c oxidase , chemistry , extracellular , biology , enzyme , organic chemistry
Cells of the green alga Selenastrum minutum display a high capacity for extra‐mitochondrial O 2 consumption in the presence of effectors such as salicylhydroxamic acid and/or NADH. We provide evidence that this O 2 consumption is mediated by extracellular peroxidase. Peroxidase capacity, measured as the potential for stimulation of O 2 consumption by a combination of salicylhydroxamic acid and NADH, changed over a 10‐day time course. Maximal stimulation of O 2 consumption occurred at day three, at which point the capacity for peroxidase‐mediated O 2 consumption was three‐to four‐fold higher than that of the control O 2 consumption rate. Peroxidase‐mediated O 2 consumption was sensitive to inhibition by 50 m M ascorbate and by cyanide. Cyanide titration curves indicated that O 2 consumption by peroxidase was much more sensitive to inhibition by cyanide than was O 2 consumption by cytochrome oxidase (I 50 < 1.6 μ M and I 50 = 18.3 μ M cyanide, respectively). By using evidence from a combination of cyanide titration curves and ascorbate inhibition, we concluded that despite a large capacity for peroxidase‐mediated O 2 consumption, peroxidase did not measurably contribute to control rates of O 2 consumption. In the absence of effectors, O 2 consumption was mediated primarily by cytochrome oxidase.