Auxin biosynthesis and its regulation on the molecular level

Kutáček, M.

doi:10.1007/bf02902152

Cited by 25 publications

(17 citation statements)

References 10 publications

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“…Second, the estimated apparent K m for Met is exceptionally low (30 m); aminotransferases typically have K m values for amino acids in the mm range (Jenkins and Fonda, 1985), and Gln and Asn aminotransferases are no exception (Cooper and Meister, 1985). The E. intestinalis enzyme is also clearly distinct from a Met-glyoxylate aminotransferase involved in glucosinolate synthesis in crucifers, which shows little activity with 2-oxoglutarate as amino acceptor (Chapple et al, 1990), and from a nonspecific, low-affinity Met aminotransferase in pea (Kutacek, 1985). Because DMSP represents about 90% of the reduced S in E. intestinalis, a high-affinity aminotransferase may be needed to sustain a high Met flux to DMSP in the face of competition for Met from AdoMet and methionyl-tRNA synthetases, which can have high affinities for Met (Burbaum and Schimmel, 1992; Schrö der et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

et al. 1998

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Many marine algae produce 3-dimethylsulfoniopropionate (DMSP), a potent osmoprotective compound whose degradation product dimethylsulfide plays a central role in the biogeochemical S cycle. Algae are known to synthesize DMSP via the four-step pathway, L-Met 3 4-methylthio-2-oxobutyrate 3 4-methylthio-2-hydroxybutyrate 3 4-dimethylsulfonio-2-hydroxy-butyrate (DM-SHB) 3 DMSP. Substrate-specific enzymes catalyzing the first three steps in this pathway were detected and partially characterized in cell-free extracts of the chlorophyte alga Enteromorpha intestinalis. The first is a 2-oxoglutarate-dependent aminotransferase, the second an NADPH-linked reductase, and the third an S-adenosylmethioninedependent methyltransferase. Sensitive radiometric assays were developed for these enzymes, and used to show that their activities are high enough to account for the estimated in vivo flux from Met to DMSP. The activities of these enzymes in other DMSP-rich chlorophyte algae were at least as high as those in E. intestinalis, but were >20-fold lower in algae without DMSP. The reductase and methyltransferase were specific for the D-enantiomer of 4-methylthio-2-hydroxybutyrate in vitro, and both the methyltransferase step and the step(s) converting DMSHB to DMSP were shown to prefer D-enantiomers in vivo. The intermediate DMSHB was shown to act as an osmoprotectant, which indicates that the first three steps of the DMSP synthesis pathway may be sufficient to confer osmotolerance.

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Section: Discussionmentioning

confidence: 99%

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

et al. 1998

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“…Although TrpDHs from higher plants require calcium or manganese ion for exhibiting their enzymatic activities (19,20), the activity of NpTrpDH was found to be not affected by divalent metal ions. The most striking feature was that NpTrpDH used L-Trp as the preferred electron donor for oxidative deamination and exhibited much less activity when L-Phe was used as the electron donor.…”

mentioning

confidence: 91%

“…The enzyme was first identified in several higher plants, including Pisum sativum, in the mid-1980s (17) and was partially characterized at that time (18)(19)(20)(21). Since then, no study was reported for this enzyme until Npun_R1275 from a cyanobacterium, Nostoc punctiforme ATCC 29133 (29133TrpDH), was identified to be the first NAD ϩ -dependent TrpDH of microbial origin (22).…”

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confidence: 99%

Structural Insights into l -Tryptophan Dehydrogenase from a Photoautotrophic Cyanobacterium, Nostoc punctiforme

Wakamatsu

Sakuraba

Kitamura

et al. 2017

Appl Environ Microbiol

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L-Tryptophan dehydrogenase from Nostoc punctiforme NIES-2108 (NpTrpDH), despite exhibiting high amino acid sequence identity (Ͼ30%)/homology (Ͼ50%) with NAD(P) ϩ -dependent L-Glu/L-Leu/L-Phe/L-Val dehydrogenases, exclusively catalyzes reversible oxidative deamination of L-Trp to 3-indolepyruvate in the presence of NAD ϩ . Here, we determined the crystal structure of the apo form of NpTrpDH. The structure of the NpTrpDH monomer, which exhibited high similarity to that of L-Glu/L-Leu/L-Phe dehydrogenases, consisted of a substrate-binding domain (domain I, residues 3 to 133 and 328 to 343) and an NAD ϩ /NADH-binding domain (domain II, residues 142 to 327) separated by a deep cleft. The apo-NpTrpDH existed in an open conformation, where domains I and II were apart from each other. The subunits dimerized themselves mainly through interactions between amino acid residues around the ␤-1 strand of each subunit, as was observed in the case of L-Phe dehydrogenase. The binding site for the substrate L-Trp was predicted by a molecular docking simulation and validated by site-directed mutagenesis. Several hydrophobic residues, which were located in the active site of NpTrpDH and possibly interacted with the side chain of the substrate L-Trp, were arranged similarly to that found in L-Leu/L-Phe dehydrogenases but fairly different from that of an L-Glu dehydrogenase. Our crystal structure revealed that Met-40, Ala-69, Ile-74, Ile-110, Leu-288, Ile-289, and Tyr-292 formed a hydrophobic cluster around the active site. The results of the site-directed mutagenesis experiments suggested that the hydrophobic cluster plays critical roles in protein folding, L-Trp recognition, and catalysis. Our results provide critical information for further characterization and engineering of this enzyme.IMPORTANCE In this study, we determined the three-dimensional structure of L-Trp dehydrogenase, analyzed its various site-directed substitution mutants at residues located in the active site, and obtained the following informative results. Several residues in the active site form a hydrophobic cluster, which may be a part of the hydrophobic core essential for protein folding. To our knowledge, there is no previous report demonstrating that a hydrophobic cluster in the active site of any L-amino acid dehydrogenase may have a critical impact on protein folding. Furthermore, our results suggest that this hydrophobic cluster could strictly accommodate L-Trp. These studies show the structural characteristics of L-Trp dehydrogenase and hence would facilitate novel applications of L-Trp dehydrogenase.

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“…Furthermore, IAA increase in the cultured ovaries allowed us to notice the importance that the ovary can regulate that levels of IAA independent of seed and other organ. Law (1987) and Kutakek (1985) demonstrated that GA3 stimulates the activity of several enzymes in the IAA biosynthesis pathway. From their suggestion, we consider that an increase in IAA-like substances content of the ovary is due to the activation of enzymes in IAA biosynthesis pathway in the ovary by GA3.…”

Section: Phytohormonesmentioning

confidence: 99%

Synergism of Gibberellin and Auxin in 'Delaware' Grape Ovary Development in Vitro

Shiozaki

Ueda

Ogata

et al. 1995

Engei Gakkai zasshi

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SummaryThe correlative effect of gibberellin A3 (GA3) and indole-3-acetic acid (IAA) on the development of 'Delaware' grape ovary was examined in vitro.GA3 induced a significant increase of the ovary fresh weight, proportionate to its concentration; IAA and tryptophan (Trp), a precursor of IAA, had little effect on increasing in fresh weight of the ovary. GA3 + IAA increased the ovary fresh weight more than GA3 or IAA alone. The fresh weights of the GA3 or IAA treated ovaries increased 1.08-to 1.56-fold over the control, whereas those treated with the combination of GA3 and IAA increased 1.85-to 2-fold over control after a 9-10 week-culture. The effect of GA3+ Trp on increasing in fresh weight of the ovary was about the same as that of GA3+IAA. These results indicate that GA3 promotes the ovary development more than IAA and that IAA and Trp enlarge the promotive effect of GA3.The ovary development in response to GA3 and GA3 + Trp was partly inhibited by anti-auxins such as N-(1-naphthyl) phthalamic acid (NPA), 2,3,5-triiodobenzoic acid (TIBA). Besides inducing an increase of the ovary fresh weight, GA3 increased the content of IAA-like substances in the ovary. From these results, it appears that the effect of GA3 on the ovary development is ascribed not only to its original action, but also to the synergistic action with IAA synthesized de novo.

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Auxin biosynthesis and its regulation on the molecular level

Cited by 25 publications

References 10 publications

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

Structural Insights into l -Tryptophan Dehydrogenase from a Photoautotrophic Cyanobacterium, Nostoc punctiforme

Synergism of Gibberellin and Auxin in 'Delaware' Grape Ovary Development in Vitro

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