Temperature adaptation of glutathione S-transferase P1-1. A case for homotropic regulation of substrate binding. |
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Authors: | A M Caccuri G Antonini P Ascenzi M Nicotra M Nuccetelli A P Mazzetti G Federici M Lo Bello G Ricci |
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Institution: | Department of Biology, University of Rome Tor Vergata, I-00133 Rome, Italy. |
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Abstract: | Human glutathione S-transferase P1-1 (GST P1-1) is a homodimeric enzyme expressed in several organs as well as in the upper layers of epidermis, playing a role against carcinogenic and toxic compounds. A sophisticated mechanism of temperature adaptation has been developed by this enzyme. In fact, above 35 degrees C, glutathione (GSH) binding to GST P1-1 displays positive cooperativity, whereas negative cooperativity occurs below 25 degrees C. This binding mechanism minimizes changes of GSH affinity for GST P1-1 because of temperature fluctuation. This is a likely advantage for epithelial skin cells, which are naturally exposed to temperature variation and, incidentally, to carcinogenic compounds, always needing efficient detoxifying systems. As a whole, GST P1-1 represents the first enzyme which displays a temperature-dependent homotropic regulation of substrate (e.g. GSH) binding. |
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