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Su Y, Michimori Y, Atomi H. Biochemical and genetic examination of two aminotransferases from the hyperthermophilic archaeon Thermococcus kodakarensis. Front Microbiol 2023; 14:1126218. [PMID: 36891395 PMCID: PMC9986279 DOI: 10.3389/fmicb.2023.1126218] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 01/31/2023] [Indexed: 02/22/2023] Open
Abstract
The hyperthermophilic archaeon Thermococcus kodakarensis utilizes amino acids as a carbon and energy source. Multiple aminotransferases, along with glutamate dehydrogenase, are presumed to be involved in the catabolic conversion of amino acids. T. kodakarensis harbors seven Class I aminotransferase homologs on its genome. Here we examined the biochemical properties and physiological roles of two Class I aminotransferases. The TK0548 protein was produced in Escherichia coli and the TK2268 protein in T. kodakarensis. Purified TK0548 protein preferred Phe, Trp, Tyr, and His, and to a lower extent, Leu, Met and Glu. The TK2268 protein preferred Glu and Asp, with lower activities toward Cys, Leu, Ala, Met and Tyr. Both proteins recognized 2-oxoglutarate as the amino acceptor. The TK0548 protein exhibited the highest k cat/K m value toward Phe, followed by Trp, Tyr, and His. The TK2268 protein exhibited highest k cat/K m values for Glu and Asp. The TK0548 and TK2268 genes were individually disrupted, and both disruption strains displayed a retardation in growth on a minimal amino acid medium, suggesting their involvement in amino acid metabolism. Activities in the cell-free extracts of the disruption strains and the host strain were examined. The results suggested that the TK0548 protein contributes to the conversion of Trp, Tyr and His, and the TK2268 protein to that of Asp and His. Although other aminotransferases seem to contribute to the transamination of Phe, Trp, Tyr, Asp, and Glu, our results suggest that the TK0548 protein is responsible for the majority of aminotransferase activity toward His in T. kodakarensis. The genetic examination carried out in this study provides insight into the contributions of the two aminotransferases toward specific amino acids in vivo, an aspect which had not been thoroughly considered thus far.
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Affiliation(s)
- Yu Su
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Yuta Michimori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Haruyuki Atomi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan.,Integrated Research Center for Carbon Negative Science, Kyoto University, Kyoto, Japan
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Kawakami R, Ohshida T, Hayashi J, Yoneda K, Furumoto T, Ohshima T, Sakuraba H. Crystal structure of a novel type of ornithine δ-aminotransferase from the hyperthermophilic archaeon Pyrococcus horikoshii. Int J Biol Macromol 2022; 208:731-740. [PMID: 35337912 DOI: 10.1016/j.ijbiomac.2022.03.114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 03/01/2022] [Accepted: 03/17/2022] [Indexed: 11/05/2022]
Abstract
Ornithine δ-aminotransferase (Orn-AT) activity was detected for the enzyme annotated as a γ-aminobutyrate aminotransferase encoded by PH1423 gene from Pyrococcus horikoshii OT-3. Crystal structures of this novel archaeal ω-aminotransferase were determined for the enzyme in complex with pyridoxal 5'-phosphate (PLP), in complex with PLP and l-ornithine (l-Orn), and in complex with N-(5'-phosphopyridoxyl)-l-glutamate (PLP-l-Glu). Although the sequence identity was relatively low (28%), the main-chain coordinates of P. horikoshii Orn-AT monomer showed notable similarity to those of human Orn-AT. However, the residues recognizing the α-amino group of l-Orn differ between the two enzymes. In human Orn-AT, Tyr55 and Tyr85 recognize the α-amino group, whereas the side chains of Thr92* and Asp93*, which arise from a loop in the neighboring subunit, form hydrogen bonds with the α-amino group of the substrate in P. horikoshii enzyme. Site-directed mutagenesis suggested that Asp93* plays critical roles in maintaining high affinity for the substrate. This study provides new insight into the substrate binding of a novel type of Orn-AT. Moreover, the structure of the enzyme with the reaction-intermediate analogue PLP-l-Glu bound provides the first structural evidence for the "Glu switch" mechanism in the dual substrate specificity of Orn-AT.
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Affiliation(s)
- Ryushi Kawakami
- Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, 2-1, Minamijosanjima-cho, Tokushima, Tokushima 770-8513, Japan
| | - Tatsuya Ohshida
- Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan
| | - Junji Hayashi
- Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University, 2-1, Minamijosanjima-cho, Tokushima, Tokushima 770-8513, Japan
| | - Kazunari Yoneda
- Department of Food and Life Sciences, School of Agriculture, Tokai University, 9-1-1 Toroku, Higashi-ku, Kumamoto-shi, Kumamoto 862-8652, Japan
| | - Toshio Furumoto
- Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan
| | - Toshihisa Ohshima
- Department of Biomedical Engineering, Faculty of Engineering, Osaka Institute of Technology, 5-16-1 Ohmiya, Asahi-ku, Osaka 535-8585, Japan
| | - Haruhiko Sakuraba
- Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan.
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