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WILD-TYPE HYDROXYCINNAMOYL-COA HYDRATASE LYASE IN COMPLEX WITH ACETYL-COA AND VANILLINWILD-TYPE HYDROXYCINNAMOYL-COA HYDRATASE LYASE IN COMPLEX WITH ACETYL-COA AND VANILLIN
Structural highlights
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 PubMedHCHL (hydroxycinnamoyl-CoA hydratase-lyase) catalyses the biotransformation of feruloyl-CoA to acetyl-CoA and the important flavour-fragrance compound vanillin (4-hydroxy-3-methoxybenzaldehyde) and is exploited in whole-cell systems for the bioconversion of ferulic acid into natural equivalent vanillin. The reaction catalysed by HCHL has been thought to proceed by a two-step process involving first the hydration of the double bond of feruloyl-CoA and then the cleavage of the resultant beta-hydroxy thioester by retro-aldol reaction to yield the products. Kinetic analysis of active-site residues identified using the crystal structure of HCHL revealed that while Glu-143 was essential for activity, Ser-123 played no major role in catalysis. However, mutation of Tyr-239 to Phe greatly increased the K(M) for the substrate ferulic acid, fulfilling its anticipated role as a factor in substrate binding. Structures of WT (wild-type) HCHL and of the S123A mutant, each of which had been co-crystallized with feruloyl-CoA, reveal a subtle helix movement upon ligand binding, the consequence of which is to bring the phenolic hydroxyl of Tyr-239 into close proximity to Tyr-75 from a neighbouring subunit in order to bind the phenolic hydroxyl of the product vanillin, for which electron density was observed. The active-site residues of ligand-bound HCHL display a remarkable three-dimensional overlap with those of a structurally unrelated enzyme, vanillyl alcohol oxidase, that also recognizes p-hydroxylated aromatic substrates related to vanillin. The data both explain the observed substrate specificity of HCHL for p-hydroxylated cinnamate derivatives and illustrate a remarkable convergence of the molecular determinants of ligand recognition between the two otherwise unrelated enzymes. A ternary complex of hydroxycinnamoyl-CoA hydratase-lyase (HCHL) with acetyl-CoA and vanillin gives insights into substrate specificity and mechanism.,Bennett JP, Bertin L, Moulton B, Fairlamb IJ, Brzozowski AM, Walton NJ, Grogan G Biochem J. 2008 Sep 1;414(2):281-9. PMID:18479250[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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