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Dong S, Wang L, Qin H, Zhan H, Wang D, Cao X. Expression Patterns and Functional Analysis of Three SmTAT Genes Encoding Tyrosine Aminotransferases in Salvia miltiorrhiza. Int J Mol Sci 2023; 24:15575. [PMID: 37958559 PMCID: PMC10649420 DOI: 10.3390/ijms242115575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/20/2023] [Accepted: 10/23/2023] [Indexed: 11/15/2023] Open
Abstract
Tyrosine aminotransferase (TAT, E.C. 2.6.1.5) is a pyridoxal phosphate-dependent aminotransferase that is widely found in living organisms. It catalyzes the transfer of the amino group on tyrosine to α-ketoglutarate to produce 4-hydroxyphenylpyruvic acid (4-HPP) and is the first enzyme for tyrosine degradation. Three SmTATs have been identified in the genome of Salvia miltiorrhiza (a model medicinal plant), but their information is very limited. Here, the expression profiles of the three SmTAT genes (SmTAT1, SmTAT2, and SmTAT3) were studied. All three genes expressed in different tissues and responded to methyl jasmonate stimuli. SmTAT proteins are localized in the cytoplasm. The recombinant SmTATs were subjected to in vitro biochemical properties. All three recombinant enzymes had TAT activities and SmTAT1 had the highest catalytic activity for tyrosine, followed by SmTAT3. Also, SmTAT1 preferred the direction of tyrosine deamination to 4-HPP, while SmTAT2 preferred transamination of 4-HPP to tyrosine. In parallel, transient overexpression of SmTATs in tobacco leaves revealed that all three SmTAT proteins catalyzed tyrosine to 4-HPP in vivo, with SmTAT1 exhibiting the highest enzymatic activity. Overall, our results lay a foundation for the production of tyrosine-derived secondary metabolites via metabolic engineering or synthetic biology in the future.
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Affiliation(s)
| | | | | | | | | | - Xiaoyan Cao
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi’an 710062, China; (S.D.); (L.W.); (H.Q.); (H.Z.); (D.W.)
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de Raad M, Koper K, Deng K, Bowen BP, Maeda HA, Northen TR. Mass spectrometry imaging-based assays for aminotransferase activity reveal a broad substrate spectrum for a previously uncharacterized enzyme. J Biol Chem 2023; 299:102939. [PMID: 36702250 PMCID: PMC9957770 DOI: 10.1016/j.jbc.2023.102939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 01/19/2023] [Accepted: 01/20/2023] [Indexed: 01/25/2023] Open
Abstract
Aminotransferases (ATs) catalyze pyridoxal 5'-phosphate-dependent transamination reactions between amino donor and keto acceptor substrates and play central roles in nitrogen metabolism of all organisms. ATs are involved in the biosynthesis and degradation of both proteinogenic and nonproteinogenic amino acids and also carry out a wide variety of functions in photorespiration, detoxification, and secondary metabolism. Despite the importance of ATs, their functionality is poorly understood as only a small fraction of putative ATs, predicted from DNA sequences, are associated with experimental data. Even for characterized ATs, the full spectrum of substrate specificity, among many potential substrates, has not been explored in most cases. This is largely due to the lack of suitable high-throughput assays that can screen for AT activity and specificity at scale. Here we present a new high-throughput platform for screening AT activity using bioconjugate chemistry and mass spectrometry imaging-based analysis. Detection of AT reaction products is achieved by forming an oxime linkage between the ketone groups of transaminated amino donors and a probe molecule that facilitates mass spectrometry-based analysis using nanostructure-initiator mass spectrometry or MALDI-mass spectrometry. As a proof-of-principle, we applied the newly established method and found that a previously uncharacterized Arabidopsis thaliana tryptophan AT-related protein 1 is a highly promiscuous enzyme that can utilize 13 amino acid donors and three keto acid acceptors. These results demonstrate that this oxime-mass spectrometry imaging AT assay enables high-throughput discovery and comprehensive characterization of AT enzymes, leading to an accurate understanding of the nitrogen metabolic network.
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Affiliation(s)
- Markus de Raad
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
| | - Kaan Koper
- Department of Botany, University of Wisconsin-Madison; Madison, Wisconsin, USA
| | - Kai Deng
- Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Emeryville, California, USA; Sandia National Laboratories, Livermore, California, USA
| | - Benjamin P Bowen
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA; Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Hiroshi A Maeda
- Department of Botany, University of Wisconsin-Madison; Madison, Wisconsin, USA
| | - Trent R Northen
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA; Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Emeryville, California, USA; Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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