Thermal Dependence of the Apparent Kmof Glutathione Reductase from Three Wetland Grasses and Maize |
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Authors: | Griffith Stephen M; Brewer Timothy G; Steiner Jeffrey J |
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Institution: | United States Department of Agriculture, Agricultural Research Service, 3450 SW Campus Way, Corvallis, Oregon 97331, USA Department of Crop and Soil Science, Oregon State University, USA |
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Abstract: | The thermal dependence of enzyme kinetic parameters has beenpresented as an indicator of species thermal optima andtolerance limits. Previous studies suggest the relationshipbetween temperature and the apparent MichaelisMentenconstant (Km) of an enzyme system can be used to predict wholeplant success at specific temperatures. The apparent Kmfor glutathionereductase (EC 1.6.4.2; GR) (oxidized glutathione as substrate)extracted from leaves of American sloughgrass (Beckmannia syzigachneSteud.), tufted hairgrass (Deschampsia caespitosa L.), tallfescue (Festuca arundinaceae Schreb. Titan), andmaize (Zea mays L.), was determined over a range of temperatures(140 °C). For all species, minimum apparent KmforGR was observed at 1 °C, and Kmvalues increased as temperatureincreased. The apparent Kmvalues differed among all speciesat the lower temperatures (115 °C), but were similarat higher temperatures. The enzyme from tufted hairgrass hadthe lowest apparent Kmat low temperatures (<15 °C), followedin increasing order by American sloughgrass, tall fescue andmaize. Our experimental system failed to reproduce thermal kineticwindow profiles similar to those reported elsewhere. With respectto the enzyme systems reported here, results suggest that thesecool-season grasses can be ranked as more to less eurythermicwithin the temperature range from 1 to 15 °C. Copyright0000 American sloughgrass, Beckmannia syzigachne Steud., tufted hairgrass, Deschampsia caespitosa L., tall fescue, Festuca arundinaceae Schreb. Titan, Zea mays L., plant competition, temperature stress, kinetics, MichaelisMenten constant (Km), glutathione reductase |
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