ORGN 519 |
| Xiyun Zhang, Department of Chemistry and Biochemistry, UCLA, MSB, Room 5440, 607 Charles E. Young Drive East, Los Angeles, CA 90095 and K. N. Houk, Department of Chemistry & Biochemistry, UCLA, 405 Hilgard Ave, Los Angeles, CA 90095-1569. |
| E. coli. D-2-deoxyribose-5-phosphate aldolase (DERA) catalyzes the reversible aldol reaction between the donor, acetaldehyde, and the acceptor, D-glyceraldehyde-3-phosphate, to generate D-2-deoxyribose-5-phosphate (DRP). Through a combination of X-ray structures, site-directed mutagenesis, and 1H NMR, Heine et al. proposed a detailed catalytic mechanism of DERA and an explanation of stereochemistry.1 Favorable electrostatic interactions are provided by many active-site residues. Asp 102, Lys 167 and Lys 201 are key residues that participate in the catalysis directly. Lys 167 functions as a nucleophile at neutral pH and attacks the substrate carbonyl carbon to form the enamine intermediate. A conserved active-site water is potential to be activated by the proton relay system (Asp 102, Lys 167 and Lys 201) and function as a critical mediator for proton transfer. While two intermediates in the mechanism have been identified by crystallography, the role of various active-site residues is not clear. Our goal is to explore how DERA catalyzes the stereoselective aldol reaction both qualitatively and quantitatively. The small ligands along the reaction pathway, including substrates, transition states, intermediates, and product, were constructed and complexed with the DERA crystal structure computationally. Molecular dynamics simulations of each complex provide some insights into how each species interacts with the enzyme and therefore how the stereoselective catalysis occurs. Quantum mechanical calculations were also carried to evaluate the energetics of both catalyzed and uncatalyzed reactions. |
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Bioorganic, Molecular Recognition, Asymmetric Reactions and Syntheses
11:00 AM-1:00 PM, Wednesday, September 10, 2003 Javits Convention Center -- Hall 1B/1C, Poster
Sci-Mix
Division of Organic Chemistry |