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MetaCyc Enzyme: tryptophan 2-monooxygenase

Gene: iaaM Accession Number: G-5821 (MetaCyc)

Species: Pseudomonas savastanoi

The oxidative decarboxylation of L-tryptophan to indole-3-acetamide, catalyzed by tryptophan 2-monooxygenase, represents a controlling reaction in the synthesis of indoleacetate by the plant pathogen Pseudomonas savastanoi. This enzyme has been purified from a strain of Pseudomonas savastanoi (strain 2009) that has been isolated from oleander plants in California, US. In this strain, the iaaM gene, which encodes this enzyme, is loacted on a 53 kb plasmid, named pIAA1 [Comai80].

The enzyme has been purified both from its native source [Kosuge66], and from a heterologous host (Escherichia coli) [Hutcheson85]. The holoenzyme contained one FAD moiety/subunit with properties consistent with a catalytic function. The enzyme activity fit simple Michaelis Menten kinetics with a Km for L-tryptophan of 50 μM. Both 3-Indoleacetamide and 3-indoleacetate were regulatory effectors for this enzymes, with apparent Ki of 7 μM, and 225 μM, respectively. At Km concentrations of tryptophan, enzyme activity was inhibited 50% by 25 μM 3-indoleacetamide, and 230 μM indoleacetate, indicating that IAA synthesis in P. savastanoi is regulated by limiting tryptophan and by feedback inhibition from indoleacetamide and indoleacette [Hutcheson85].

Gene Citations: [Yamada85]

Molecular Weight of Polypeptide: 61.861 kD (from nucleotide sequence), 62 kD (experimental) [Hutcheson85 ]

Unification Links: ModBase:P06617 , Protein Model Portal:P06617 , Swiss-Model:P06617 , UniProt:P06617

Relationship Links: Entrez-Nucleotide:RELATED-TO:M11035 , InterPro:IN-FAMILY:IPR002937 , PDB:Structure:4IV9 , Pfam:IN-FAMILY:PF01593

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

MultiFun Terms: metabolism carbon utilization amino acids

Enzymatic reaction of: tryptophan 2-monooxygenase

EC Number:

L-tryptophan + oxygen <=> indole-3-acetamide + CO2 + H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

Alternative Substrates for L-tryptophan: 5-hydroxy-L-tryptophan [Kosuge66 ]

In Pathways: indole-3-acetate biosynthesis III (bacteria)

Cofactors or Prosthetic Groups: FAD [Hutcheson85]

Inhibitors (Other): indole-3-acetamide [Kosuge66]

Inhibitors (Unknown Mechanism): Hg2+ [Kosuge66] , hydroxylamine [Kosuge66] , iodoacetamide [Kosuge66] , indole-3-acetate [Kosuge66]

Primary Physiological Regulators of Enzyme Activity: indole-3-acetate , indole-3-acetamide

Kinetic Parameters:

Km (μM)


Comai80: Comai L, Kosuge T (1980). "Involvement of plasmid deoxyribonucleic acid in indoleacetic acid synthesis in Pseudomonas savastanoi." J Bacteriol 143(2);950-7. PMID: 7204339

Hutcheson85: Hutcheson SW, Kosuge T (1985). "Regulation of 3-indoleacetic acid production in Pseudomonas syringae pv. savastanoi. Purification and properties of tryptophan 2-monooxygenase." J Biol Chem 260(10);6281-7. PMID: 3997822

Kosuge66: Kosuge T, Heskett MG, Wilson EE (1966). "Microbial synthesis and degradation of indole-3-acetic acid. I. The conversion of L-tryptophan to indole-3-acetamide by an enzyme system from Pseudomonas savastanoi." J Biol Chem 241(16);3738-44. PMID: 5916389

Yamada85: Yamada, T., Palm, C. J., Brooks, B., Kosuge, T. (1985). "Nucleotide sequences of the Pseudomonas savastanoi indoleacetic acid genes show homology with the Agrobacterium tumefaciens T-DNA." Proc. Natl. Acad. USA 82:6522-6526.

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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