The Respiratory Chain of Plant Mitochondria VII. Kinetics of Flavoprotein Oxidation in Skunk Cabbage Mitochondria

The Respiratory Chain of Plant Mitochondria VII. Kinetics of Flavoprotein Oxidation in Skunk... Maria Erecinska and Bayard T. Storey a Johnson Research Foundation, University of Pennsylvania, Philadelphia, Pennsylvania 19104 Abstract The oxidation kinetics of the two high potential flavo-proteins, one (Fp hf ) fluorescent and the other (Fp ha ) nonfluorescent, in mitochondria from skunk cabbage ( Symplocarpus foetidus ) spadices have been measured by combined spectrophotometry and fluorimetry. In the absence of respiratory inhibitors, both flavoproteins are oxidized at nearly the same rate with half-times between 120 and 160 milliseconds at 24 C. When slight differences in rate are observed, it is Fp ha which consistently has the shorter half-time. The presence of 0.3 millimolar KCN has no perceptible effect on the oxidation rate of either component. Antimycin A (2 nanomoles per milligram of protein) increases the oxidation half-time of Fp ha about 3-fold, but it has no effect on the oxidation half-time of Fp hf . In contrast to these two inhibitors, m -chlorobenzhydroxamic acid—an inhibitor specific to the cyanide insensitive, alternate oxidase pathway in these mitochondria—increases the oxidation half-time of Fp hf 10-fold to about 2 seconds, while increasing that of Fp ha only some 20%. This result implies that the flavoprotein Fp hf mediates electron transport to the alternate oxidase from the region of the mitochondrial respiratory chain encompassing Fp ha , ubiquinone, and the cytochromes b. The oxidation rate of cytochrome b 557 is unaffected by either m -chlorobenzhydroxamic acid or cyanide but is strongly inhibited by antimycin A. This result implies that cytochrome b 557 plays no direct role in the respiratory pathway to the alternate oxidase and is different from cytochrome b 7 found in mitochondria from the spadices of Arum maculatum. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

The Respiratory Chain of Plant Mitochondria VII. Kinetics of Flavoprotein Oxidation in Skunk Cabbage Mitochondria

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Publisher
American Society of Plant Biologist
Copyright
Copyright © 1970 by the American Society of Plant Biologists
ISSN
1532-2548
eISSN
0032-0889
DOI
10.1104/pp.46.4.618
Publisher site
See Article on Publisher Site

Abstract

Maria Erecinska and Bayard T. Storey a Johnson Research Foundation, University of Pennsylvania, Philadelphia, Pennsylvania 19104 Abstract The oxidation kinetics of the two high potential flavo-proteins, one (Fp hf ) fluorescent and the other (Fp ha ) nonfluorescent, in mitochondria from skunk cabbage ( Symplocarpus foetidus ) spadices have been measured by combined spectrophotometry and fluorimetry. In the absence of respiratory inhibitors, both flavoproteins are oxidized at nearly the same rate with half-times between 120 and 160 milliseconds at 24 C. When slight differences in rate are observed, it is Fp ha which consistently has the shorter half-time. The presence of 0.3 millimolar KCN has no perceptible effect on the oxidation rate of either component. Antimycin A (2 nanomoles per milligram of protein) increases the oxidation half-time of Fp ha about 3-fold, but it has no effect on the oxidation half-time of Fp hf . In contrast to these two inhibitors, m -chlorobenzhydroxamic acid—an inhibitor specific to the cyanide insensitive, alternate oxidase pathway in these mitochondria—increases the oxidation half-time of Fp hf 10-fold to about 2 seconds, while increasing that of Fp ha only some 20%. This result implies that the flavoprotein Fp hf mediates electron transport to the alternate oxidase from the region of the mitochondrial respiratory chain encompassing Fp ha , ubiquinone, and the cytochromes b. The oxidation rate of cytochrome b 557 is unaffected by either m -chlorobenzhydroxamic acid or cyanide but is strongly inhibited by antimycin A. This result implies that cytochrome b 557 plays no direct role in the respiratory pathway to the alternate oxidase and is different from cytochrome b 7 found in mitochondria from the spadices of Arum maculatum.

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