|
|
| Line 1: |
Line 1: |
| [[Image:1b15.gif|left|200px]] | | {{Seed}} |
| | [[Image:1b15.png|left|200px]] |
|
| |
|
| <!-- | | <!-- |
| Line 9: |
Line 10: |
| {{STRUCTURE_1b15| PDB=1b15 | SCENE= }} | | {{STRUCTURE_1b15| PDB=1b15 | SCENE= }} |
|
| |
|
| '''ALCOHOL DEHYDROGENASE FROM DROSOPHILA LEBANONENSIS TERNARY COMPLEX WITH NAD-ACETONE'''
| | ===ALCOHOL DEHYDROGENASE FROM DROSOPHILA LEBANONENSIS TERNARY COMPLEX WITH NAD-ACETONE=== |
|
| |
|
|
| |
|
| ==Overview==
| | <!-- |
| Drosophila alcohol dehydrogenase (DADH) is an NAD+-dependent enzyme that catalyzes the oxidation of alcohols to aldehydes/ketones. DADH is the member of the short-chain dehydrogenases/reductases family (SDR) for which the largest amount of biochemical data has been gathered during the last three decades. The crystal structures of one binary form (NAD+) and three ternary complexes with NAD+.acetone, NAD+.3-pentanone and NAD+.cyclohexanone were solved at 2.4, 2.2, 1. 4 and 1.6 A resolution, respectively. From the molecular interactions observed, the reaction mechanism could be inferred. The structure of DADH undergoes a conformational change in order to bind the coenzyme. Furthermore, upon binding of the ketone, a region that was disordered in the apo form (186-191) gets stabilized and closes the active site cavity by creating either a small helix (NAD+. acetone, NAD+.3-pentanone) or an ordered loop (NAD+.cyclohexanone). The active site pocket comprises a hydrophobic bifurcated cavity which explains why the enzyme is more efficient in oxidizing secondary aliphatic alcohols (preferably R form) than primary ones. Difference Fourier maps showed that the ketone inhibitor molecule has undergone a covalent reaction with the coenzyme in all three ternary complexes. Due to the presence of the positively charged ring of the coenzyme (NAD+) and the residue Lys155, the amino acid Tyr151 is in its deprotonated (tyrosinate) state at physiological pH. Tyr151 can subtract a proton from the enolic form of the ketone and catalyze a nucleophilic attack of the Calphaatom to the C4 position of the coenzyme creating an NAD-ketone adduct. The binding of these NAD-ketone adducts to DADH accounts for the inactivation of the enzyme. The catalytic reaction proceeds in a similar way, involving the same amino acids as in the formation of the NAD-ketone adduct. The p Kavalue of 9-9.5 obtained by kinetic measurements on apo DADH can be assigned to a protonated Tyr151 which is converted to an unprotonated tyrosinate (p Ka7.6) by the influence of the positively charged nicotinamide ring in the binary enzyme-NAD+form. pH independence during the release of NADH from the binary complex enzyme-NADH can be explained by either a lack of electrostatic interaction between the coenzyme and Tyr151 or an apparent p Kavalue for this residue higher than 10.0.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10366509}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10366509 is the PubMed ID number. |
| | --> |
| | {{ABSTRACT_PUBMED_10366509}} |
|
| |
|
| ==About this Structure== | | ==About this Structure== |
| Line 35: |
Line 39: |
| [[Category: Short-chain dehydrogenases/reductase]] | | [[Category: Short-chain dehydrogenases/reductase]] |
| [[Category: Ternary complex]] | | [[Category: Ternary complex]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 10:56:46 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 18:01:34 2008'' |