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Function(s) and Biological Relevance

Lignostilbene-α,β-dioxygenase (LsdA) from the bacterium 'Sphingomonas paucimobilis'. It is a nonheme iron oxygenase that catalyzes the cleavage of lignostilbene, a compound arising in lignin transformation, to two vanillin molecules. The substrate for this enzyme is lignostilbene. Phenylazophenol inhibited the LsdA-catalyzed cleavage of lignostilbene in a reversible, mixed fashion. Lignin is used in biofuel production. Lignin is a heterogeneous aromatic polymer found in plant cell walls that contributes to the recalcitrance of biomass. Below are two images. On the left is Lignostilbene, and on the right is Vanillin for comparison.

Broader Implications

To examine LsdA’s substrate specificity, we heterologously produced the dimeric enzyme with the help of chaperones. When tested on several substituted stilbenes, LsdA exhibited the greatest specificity for lignostilbene. These experiments further indicated that the substrate’s 4-hydroxy moiety is required for catalysis and that this moiety cannot be replaced with a methoxy group. This expands our mechanistic understanding of LsdA and related stilbene-cleaving dioxygenases.

Structural highlights and structure-function relationships

The of this protein is primarily made of the amino acids that are the main factor in catalysis. The 3 amino acids are Phe-59, Tyr101, and Lys-134. The allows us to see the different binding sites for this protein, the binding sites are allosteric. The is a fold of LsdA of a seven-bladed -propeller, typical of the carotenoid cleavage oxygenates (CCO's), which typically catalyze the oxidative cleavage of a double bond in carotenoids. The and space-filling view of the ligand in the protein, shows that both hydrophilic and hydrophobic residues are important to the ligand in the binding site.

Energy Transformation

Phenylazophenol inhibits the LsdA-catalyzed cleavage of lignostilbene in a reversible, mixed fashion.