archives@tulane.edu / β-glucosidase from the hyperthermophilic T. maritima is a retaining family 1 glycohydrolase. The action of this enzyme has been examined against a series of synthesized phenyl glucosides to construct Brønsted plots. The plot of kcat vs pKa exhibits a concave down shape suggesting a change in the rate limiting step from glycosylation to de-glycosylation. Aglycones with pKa<8 show little dependence on leaving group ability, while the poorer substrates for kcat (βlg=-0.39) and all substrates for kcat/KM (βlg=-0.41) were found to depend on leaving group ability to a similar extent. This is consistent with glycosylation being the committed step in catalysis. Solvent kinetic isotope effect studies showed that activity on para nitrophenyl glucoside (pKa=7.15) was unaffected while phenyl glucoside (pKa=9.95) was cleaved more slowly in deuterium oxide (kL/kH=1.54). Solvent kinetic isotope effects saw little change between measurement at 25 and 60 °C. This work suggests a dissociative glycosylation transition state that is stabilized in part by proton donation and a de-glycosylation transition state that involves no proton transfer. / 1 / Ross Zaenglein
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_122037 |
| Date | January 2021 |
| Contributors | Zaenglein, Ross (author), Byers, Lary (Thesis advisor), School of Science & Engineering Chemistry (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic, pages: 75 |
| Rights | No embargo, Copyright is in accordance with U.S. Copyright law. |
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