Structural highlights
Function
HCHL_PSEFL Catalyzes the hydration of the acyl-CoA thioester of ferulic acid and the subsequent retro-aldol cleavage of the hydrated intermediate to yield vanillin (4-hydroxy-3-methoxy-benzaldehyde).[1]
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 PubMed
HCHL (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[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Gasson MJ, Kitamura Y, McLauchlan WR, Narbad A, Parr AJ, Parsons EL, Payne J, Rhodes MJ, Walton NJ. Metabolism of ferulic acid to vanillin. A bacterial gene of the enoyl-SCoA hydratase/isomerase superfamily encodes an enzyme for the hydration and cleavage of a hydroxycinnamic acid SCoA thioester. J Biol Chem. 1998 Feb 13;273(7):4163-70. PMID:9461612
- ↑ Bennett JP, Bertin L, Moulton B, Fairlamb IJ, Brzozowski AM, Walton NJ, Grogan G. A ternary complex of hydroxycinnamoyl-CoA hydratase-lyase (HCHL) with acetyl-CoA and vanillin gives insights into substrate specificity and mechanism. Biochem J. 2008 Sep 1;414(2):281-9. PMID:18479250 doi:10.1042/BJ20080714
