Sweet almond beta-glucosidase is a retaining, family 1, glycosidase that catalyzes the efficient hydrolysis of a broad range of substrates. The catalytic activity of the enzyme relies on two glutamic acid residues in the active site, one protonated and the other deprotonated. The hydrolysis of p-nitrophenyl beta-D-glucoside was found to rely on two groups with pKas of 4.00 and 7.10 with a (kcat/K M)lim value of 30,902 M-1 sec-1 , in agreement with the active site containing two carboxylic acid residues Hydrolysis and binding studies for a number of glucosides were carried out over a wide temperature range to determine thermodynamic parameters for the catalyzed reactions. These studies were used to determine what effects the enthalpy and entropy of activation have on increasing the rate of the reaction during catalysis. Results indicate that the significant rate improvement is due primarily to a more favorable enthalpy of activation for the catalyzed reaction resulting in rate enhancements between 1012-10 14 times faster than the spontaneous reactions at 25°C. The relative order of the first-order rate constants roughly follows the order predicted based on a Bronsted coefficient of -1, calculated under the assumption that the generally accepted mechanism is the correct mechanism for the substrates studied / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_23328 |
| Date | January 2011 |
| Contributors | Rountree, Margaret (Author), Mullin, David (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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