The effect of low temperatures on enzyme activity.
The stability of two enzymes from extreme thermophiles (glutamate dehydrogenase from Thermococcales strain AN1 and beta-glucosidase from Caldocellum saccharolyticum expressed in Escherichia coli) has been exploited to allow measurement of activity over a 175 degrees C temperature range, from +90 degrees C to -85 degrees C for the glutamate dehydrogenase and from +90 degrees C to -70 degrees C for the beta-glucosidase. The Arrhenius plots of these enzymes, and those for two mesophilic enzymes (glutamate dehydrogenase from bovine liver and beta-galactosidase from Escherichia coli), exhibit no downward deflection corresponding to the glass transition, found by biophysical measurements of several non-enzymic mesophilic proteins at about -65 degrees C and reflecting a sharp decrease in protein flexibility as the overall motion of groups of atoms ceases.
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Thermophile Research Unit, University of Waikato, Hamilton, New Zealand.
Daniel
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Petach
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D000818:Animals; D001105:Archaea / Q000201:enzymology; D001421:Bacteria, Anaerobic / Q000201:enzymology; D001426:Bacterial Proteins / Q000378:metabolism; D002417:Cattle; D003080:Cold Temperature; D004795:Enzyme Stability; D004798:Enzymes / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D001616:beta-Galactosidase / Q000378:metabolism; D001617:beta-Glucosidase / Q000378:metabolism
D001426:Bacterial Proteins; D004798:Enzymes; D005969:Glutamate Dehydrogenase; D001617:beta-Glucosidase; D001616:beta-Galactosidase