A single amino acid substitution in aromatic hydroxylase (HpaB) of Escherichia coli alters substrate specificity of the structural isomers of hydroxyphenylacetate.

The arginine residue at position 379 of HpaB is critical for 3HPA recognition. Information regarding the effect of amino acid residues on the substrate specificity of structural isomers can facilitate in designing hydoxylases with high catalytic efficiency and versatility.