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Indole-3-pyruvic acid regulates TAA1 activity, which plays a key role in coordinating the two steps of auxin biosynthesis.

ABSTRACT: Auxin biosynthesis involves two types of enzymes: the Trp aminotransferases (TAA/TARs) and the flavin monooxygenases (YUCCAs). This two-step pathway is highly conserved throughout the plant kingdom and is essential for almost all of the major developmental processes. Despite their importance, it is unclear how these enzymes are regulated and how their activities are coordinated. Here, we show that TAA1/TARs are regulated by their product indole-3-pyruvic acid (IPyA) (or its mimic KOK2099) via negative feedback regulation in Arabidopsis thaliana. This regulatory system also functions in rice and tomato. This negative feedback regulation appears to be achieved by both the reversibility of Trp aminotransferase activity and the competitive inhibition of TAA1 activity by IPyA. The K_m value of IPyA is 0.7 µM, and that of Trp is 43.6 µM; this allows IPyA to be maintained at low levels and prevents unfavorable nonenzymatic indole-3-acetic acid (IAA) formation from IPyA in vivo. Thus, IPyA levels are maintained by the push (by TAA1/TARs) and pull (by YUCCAs) of the two biosynthetic enzymes, in which TAA1 plays a key role in preventing the over- or under-accumulation of IPyA. TAA1 prefer Ala among various amino acid substrates in the reverse reaction of auxin biosynthesis, allowing TAA1 to show specificity for converting Trp and pyruvate to IPyA and Ala, and the reverse reaction.

SUBMITTER: Sato A

PROVIDER: S-EPMC9231625 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature

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Indole-3-pyruvic acid regulates TAA1 activity, which plays a key role in coordinating the two steps of auxin biosynthesis.

Sato Akiko A Soeno Kazuo K Kikuchi Rie R Narukawa-Nara Megumi M Yamazaki Chiaki C Kakei Yusuke Y Nakamura Ayako A Shimada Yukihisa Y

Proceedings of the National Academy of Sciences of the United States of America 20220613 25

Auxin biosynthesis involves two types of enzymes: the Trp aminotransferases (TAA/TARs) and the flavin monooxygenases (YUCCAs). This two-step pathway is highly conserved throughout the plant kingdom and is essential for almost all of the major developmental processes. Despite their importance, it is unclear how these enzymes are regulated and how their activities are coordinated. Here, we show that TAA1/TARs are regulated by their product indole-3-pyruvic acid (IPyA) (or its mimic KOK2099) via ne ...[more]

PMID: 35696560

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Project description:BackgroundIndole pyruvic acid (IPA) is a versatile platform intermediate and building block for a number of high-value products in the pharmaceutical and food industries. It also has a wide range of applications, such as drugs for the nervous system, cosmetics, and luminophores. Chemical synthesis of IPA is a complicated and costly process. Moreover, through the biosynthesis route employing L-amino acid oxidase, the byproduct hydrogen peroxide leads the degradation of IPA. TdiD, identified as a specific tryptophan aminotransferase, could be an alternative solution for efficient IPA biosynthesis.ResultsEscherichia coli strain W3110, which demonstrates basic production when supplied with tryptophan, was engineered for IPA biosynthesis. Several strategies were implemented to improve IPA production. First, through incorporating the codon-optimized tdiD into W3110, IPA levels increased from 41.54 ± 1.26 to 52.54 ± 2.08 mg/L. Second, after verifying the benefit of an increased phenylpyruvate pool, a YL03 strain was constructed based on a previously reported mutant strain of W3110 with a plasmid carrying aroF fbr and pheA fbr to further improve IPA production. The recombinant YL03 strain accumulated IPA at 158.85 ± 5.36 mg/L, which was 3.82-fold higher than that of the wild-type W3110 strain. Third, optimization of tdiD co expression was carried out by replacing the Trc promoter with a series of constitutively active promoters along with increasing the plasmid copy numbers. The highest IPA production was observed in YL08, which achieved 236.42 ± 17.66 mg/L and represented a greater than 5-fold increase as compared to W3110. Finally, the effects of deletion and overexpression of tnaA on IPA biosynthesis were evaluated. The removal of tnaA led to slightly reduced IPA levels, whereas the overexpression of tnaA resulted in a considerable decline in production.ConclusionsThis study illustrates the feasibility of IPA biosynthesis in E. coli through tdiD. An efficient IPA producing strain, YL08, was developed, which provides a new possibility for biosynthesis of IPA. Although the final production was limited, this study demonstrates a convenient method of IPA synthesis.

Dataset Information

Indole-3-pyruvic acid regulates TAA1 activity, which plays a key role in coordinating the two steps of auxin biosynthesis.

Publications

Indole-3-pyruvic acid regulates TAA1 activity, which plays a key role in coordinating the two steps of auxin biosynthesis.

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