Abstract Detail


Elliott, Jorja [1], Quispe, Naomi [1], Maricle, Brian [2].

Effects of sulfide, ethanol, and lactic acid on cytochrome c oxidase and citrate synthase activities in plant roots.

Sulfide, ethanol, and lactic acid are well known as metabolic toxins, yet specific effects on respiration enzymes have not been characterized. The objective of this study was to analyze sulfide, ethanol, and lactic acid toxicity on activities of the enzymes cytochrome c oxidase (CytOx), active in oxidative phosphorylation and citrate synthase (CS), active in the citric acid cycle in mitochondria. Enzyme activity was measured in tissue homogenates from roots of several plant species in the presence of sulfide (0 to 20 µM), ethanol (0 to 100 mM), and lactic acid (0 to 100 mM). Increasing concentrations of sulfide and lactic acid significantly decreased activity in CytOx, however sulfide toxicity had a greater effect on the enzyme compared to lactic acid toxicity. Sulfide was a potent metabolic toxin; activity of CytOx was measured as high as 0.106 μmol min-1 g-1 in the absence of sulfide, but was reduced to nearly undetectable at 10 µM sulfide. CytOx activity was also reduced by lactic acid but the inhibition constant (Ki) was 104 times that of sulfide toxicity. Increasing lactic acid concentrations caused a threshold response, where CytOx was not affected until 100 mM lactic acid. Ethanol had no effect on CytOx activity. CS activity was not affected by lactic acid and only marginally affected by ethanol. Both sulfide and lactic acid influenced activities of CytOx, but to different degrees, indicating environmental and physiological constraints on plant metabolism, particularly with respect to sulfide exposure and its effects on respiration.

1 - Fort Hays State University, Department of Biological Sciences, 600 Park St., Hays, Kansas, 67601, United States
2 - Fort Hays State University, Department Of Biological Sciences, 600 Park St., Hays, KS, 67601, United States

metabolic toxin
respiration enzyme
inhibition constant.

Presentation Type: Poster This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PPE009
Abstract ID:744
Candidate for Awards:Physiological Section Best poster presentation,Physiological Section Physiological Section Li-COR Prize

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