title: Lysine ε-aminotransferases: kinetic constants, substrate specificities, and the variation in active site residues.
abstract: L-Lysine ε-aminotransferase (lysAT) is an important enzyme in tailoring the terminal amino group of L-lysine or L-ornithine and can be directed to the synthesis of various value-added chemicals such as adipic acid. Three lysATs, lysAT from Saccharopolyspora erythraea NRRL 2338 (lysAT_Sery), lysAT from Nocardia farcinica IFM 10152, and lysAT from Rhodococcus jostii RHA1, were cloned, and their kinetic values and substrate specificities were investigated. In the reaction using 5mM L-lysine and 10mM α-ketoglutarate, lysAT_Sery from S. erythraea NRRL 2338 showed 72% higher specific activity than lysAT from Nocardia farcinica IFM 10152 and 42% higher specific activity than lysAT from R. jostii RHA1. More interesting result was that lysAT Sery, exhibiting the highest activity among three lysATs, did not show any activity to L-ornithine. The alignment of 146 lysAT sequences from RefSeq database was searched by the EC number of lysAT to compare the active site residues among the lysAT sequences. The sequence alignment showed that only two residues, corresponding to Ala129 and Asn328 of lysAT from Mycobacterium tuberculosis H37Rv (lysAT_Mtub), showed variations among the active site residues. All the active site residues except those two residues were completely conserved throughout 145 lysAT sequences. lysAT from S. erythraea NRRL 2338 has A129T and N328S variations (residue numbers are those of the crystal structure of lysAT_Mtub). The structural analysis by the homology model indicate that Thr126 by A129T variation in lysAT_Sery is appeared to interact more tightly with the phosphate group of PLP than alanine (the distance between Thr126 and the phosphate group of PLP was 2.92Å). In addition, Ser328 is located at the substrate recognition site of active site and, therefore, N328S variation may be connected to the substrate specificity of lysAT.
authors.affiliation: School of Chemical and Biological Engineering and Institute of Bioengineering, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Joo-Hyun
authors.initials: JH
authors.lastname: Seo
authors.affiliation: School of Chemical and Biological Engineering and Institute of Bioengineering, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Eun-Mi
authors.initials: EM
authors.lastname: Kim
authors.affiliation: School of Chemical and Biological Engineering and Institute of Bioengineering, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Ahram
authors.initials: A
authors.lastname: Chae
authors.affiliation: School of Chemical and Biological Engineering and Institute of Bioengineering, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: byungkim@snu.ac.kr.
authors.forename: Byung-Gee
authors.initials: BG
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain / Q000235:genetics; D014644:Genetic Variation; D007700:Kinetics; D051306:L-Lysine 6-Transaminase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009615:Nocardia / Q000201:enzymology / Q000235:genetics; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012240:Rhodococcus / Q000201:enzymology / Q000235:genetics; D016930:Saccharopolyspora / Q000201:enzymology / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D051306:L-Lysine 6-Transaminase; D008239:Lysine
keywords: Enzyme characterization; Kinetic constants; Lysine ε-aminotransferase; Sequence analysis; Structural analysis; Substrate specificity