3-Hydroxybenzoate 6-hydroxylase from Klebsiella pneumoniae M5a1 is an enzyme that utilizes 3-hydroxybenzoate (3-HBA) as substrate yielding gentisate. Site-directed mutagenesis was carried out to define which residues may be involved in catalytic reaction. Substitution of arginine to glutamate at position 169 of the enzyme resulted in the complete loss of catalytic activity. This indicated Arg169 may play an important role in 3-HBA 6-hydroxylase catalysis.
Liu, D. Q., Liu, H., Gao, X. L., Leak, D. J., & Zhou, N. Y. (2005). Arg169 is essential for catalytic activity of 3-hydroxybenzoate 6-hydroxylase from Klebsiella pneumoniae M5a1. Microbiological Research, 160(1), 53-59. https://doi.org/10.1016/j.micres.2004.09.003