title: Purification and characterization of the ncgl2923 -encoded 3-hydroxybenzoate 6-hydroxylase from Corynebacterium glutamicum.
abstract: Corynebacterium glutamicum ATCC 13032 metabolizes 3-hydroxybenzoate via gentisate. We have now characterized the ncgl2923 -encoded 3-hydroxybenzoate 6-hydroxylase involved in the initial step of 3-hydroxybenzoate catabolism by this strain, a first 3-hydroxybenzoate 6-hydroxylase molecularly and biochemically characterized from a Gram-positive strain. The ncg12923 gene from Corynebacterium glutamicum ATCC 13032 was shown to encode 3-hydroxybenzoate 6-hydroxylase, the enzyme that catalyzes the NADH-dependent conversion of 3-hydroxybenzoate to gentisate. Ncgl2923 was expressed with an N-terminal six-His tag and purified to apparent homogeneity by Ni²(+)-nitrilotriacetic acid affinity chromatography. The purified H₆-Ncgl2923 showed a single band at apparent molecular mass of 49 kDa on a sodium dodecyl sulfate polyacrylamide gel electrophoresis and was found to be most likely a trimer as determined by gel filtration chromatography. It had a specific activity of 6.92 ± 0.39 U mg⁻¹ against 3-hydroxybenzoate and with a K(m) value of 53.4 ± 4.7 μM using NADH as a cofactor. The product formed from the 3-hydroxybenzoate hydroxylation catalyzed by H₆-Ncgl2923 was identified by high-performance liquid chromatography as gentisate, a ring-cleavage substrate in the microbial aromatic degradation. The enzyme exhibited a maximum activity at pH 7.5 in phosphate buffer, and adding flavin adenine dinucleotide to a final concentration of 15 μM would enhance the activity by three-fold. Although this enzyme shares no more than 33% identity with any of reported 3-hydroxybenzoate 6-hydroxylases from Gram-negative bacterial strains, there is little difference in subunit sizes and biochemical characteristics between them.
authors.affiliation: Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
authors.forename: Yi-Fan
authors.initials: YF
authors.lastname: Yang
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Zhang
authors.forename: Song-He
authors.initials: SH
authors.lastname: Wang
authors.forename: Ning-Yi
authors.initials: NY
authors.lastname: Zhou
mesh_terms: D000595:Amino Acid Sequence; D002021:Buffers; D002846:Chromatography, Affinity / Q000379:methods; D002850:Chromatography, Gel; D003067:Coenzymes / Q000378:metabolism; D048230:Corynebacterium glutamicum / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005841:Gentisates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D062385:Hydroxybenzoates / Q000378:metabolism; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D055503:Protein Multimerization; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D002021:Buffers; D003067:Coenzymes; D005841:Gentisates; D062385:Hydroxybenzoates; D011993:Recombinant Fusion Proteins; D005182:Flavin-Adenine Dinucleotide; C032948:3-hydroxybenzoic acid; D006899:Mixed Function Oxygenases; C023315:3-hydroxybenzoate-6-hydroxylase; C010925:2,5-dihydroxybenzoic acid