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| {{STRUCTURE_2vss| PDB=2vss | SCENE= }} | | {{STRUCTURE_2vss| PDB=2vss | SCENE= }} |
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| '''WILD-TYPE HYDROXYCINNAMOYL-COA HYDRATASE LYASE IN COMPLEX WITH ACETYL-COA AND VANILLIN'''
| | ===WILD-TYPE HYDROXYCINNAMOYL-COA HYDRATASE LYASE IN COMPLEX WITH ACETYL-COA AND VANILLIN=== |
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| ==Overview==
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| Hydroxycinnamoyl-CoA Hydratase-Lyase (HCHL) 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 to 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, 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 whilst Glu-143 was essential for activity, Ser-123 played no major role in catalysis. However, mutation of Tyr-239 to Phe greatly increased the KM for the substrate ferulic acid, fulfilling its anticipated role as a factor in substrate binding. Structures of wild-type HCHL and of the Ser123Ala mutant, each of which had been co-crystallised 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 with 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 recognises para-hydroxylated aromatic substrates related to vanillin. The data both explain the observed substrate specificity of HCHL for para-hydroxylated cinnamate derivatives and illustrate a remarkable convergence of the molecular determinants of ligand recognition between two otherwise unrelated enzymes.
| | The line below this paragraph, {{ABSTRACT_PUBMED_18479250}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 18479250 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_18479250}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Hydratase]] | | [[Category: Hydratase]] |
| [[Category: Lyase]] | | [[Category: Lyase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed May 28 09:16:57 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 13:24:48 2008'' |
