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| [[Image:2gd2.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2gd2| PDB=2gd2 | SCENE= }} | | {{STRUCTURE_2gd2| PDB=2gd2 | SCENE= }} |
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| '''The 1,1-proton transfer reaction mechanism by alpha-methylacyl-CoA racemase is catalyzed by an aspartate/histidine pair and involves a smooth, methionine-rich surface for binding the fatty acyl moiety'''
| | ===The 1,1-proton transfer reaction mechanism by alpha-methylacyl-CoA racemase is catalyzed by an aspartate/histidine pair and involves a smooth, methionine-rich surface for binding the fatty acyl moiety=== |
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| ==Overview==
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| Alpha-methylacyl-CoA racemases are essential enzymes for branched-chain fatty acid metabolism. Their reaction mechanism and the structural basis of their wide substrate specificity are poorly understood. High-resolution crystal structures of Mycobacterium tuberculosis alpha-methylacyl-CoA racemase (MCR) complexed with substrate molecules show the active site geometry required for catalysis of the interconversion of (2S) and (2R)-methylacyl-CoA. The thioester oxygen atom and the 2-methyl group are in a cis-conformation with respect to each other. The thioester oxygen atom fits into an oxyanion hole and the 2-methyl group points into a hydrophobic pocket. The active site geometry agrees with a 1,1-proton transfer mechanism in which the acid/base-pair residues are His126 and Asp156. The structures of the complexes indicate that the acyl chains of the S-substrate and the R-substrate bind in an S-pocket and an R-pocket, respectively. A unique feature of MCR is a large number of methionine residues in the acyl binding region, located between the S-pocket and the R-pocket. It appears that the (S) to (R) interconversion of the 2-methylacyl chiral center is coupled to a movement of the acyl group over this hydrophobic, methionine-rich surface, when moving from its S-pocket to its R-pocket, whereas the 2-methyl moiety and the CoA group remain fixed in their respective pockets.
| | The line below this paragraph, {{ABSTRACT_PUBMED_17320106}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 17320106 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_17320106}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Proton transfer]] | | [[Category: Proton transfer]] |
| [[Category: Racemase]] | | [[Category: Racemase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 04:58:02 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 08:54:55 2008'' |
