2gci
From Proteopedia
The 1,1-proton transfer reaction mechanism by alpha-methylacyl-CoA racemase is catalyzed by an asparte/histidine pair and involves a smooth, methionine-rich surface for binding the fatty acyl moiety
Structural highlights
FunctionAMACR_MYCTU Catalyzes the epimerization of (2R)- and (2S)-methylacyl-coenzyme A (CoA) thioesters (PubMed:15632186, PubMed:19854148, PubMed:26348625). Accepts as substrates a wide range of alpha-methylacyl-CoAs, including (2R)-2-methylmyristoyl-CoA and (2S)-2-methylmyristoyl-CoA, (2R)-pristanoyl-CoA and (2S)-pristanoyl-CoA, and the cholesterol esters (25R)-3-oxo-cholest-4-en-26-oyl-CoA and (25S)-3-oxo-cholest-4-en-26-oyl-CoA (PubMed:15632186, PubMed:26348625). Can also catalyze the interconversion of the non-physiologic substrates (2R)-ibuprofenoyl-CoA and (2S)-ibuprofenoyl-CoA, which are potential competitive inhibitors of the enzyme (PubMed:19854148).[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAlpha-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 catalysis of the 1,1-proton transfer by alpha-methyl-acyl-CoA racemase is coupled to a movement of the fatty acyl moiety over a hydrophobic, methionine-rich surface.,Bhaumik P, Schmitz W, Hassinen A, Hiltunen JK, Conzelmann E, Wierenga RK J Mol Biol. 2007 Apr 6;367(4):1145-61. Epub 2007 Jan 27. PMID:17320106[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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