|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 ]
|MultiFun Terms:||metabolism → carbon utilization → amino acids|
Enzymatic reaction of: tryptophan 2-monooxygenase
EC Number: 18.104.22.168
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.
The reaction is physiologically favored in the direction shown.
In Pathways: indole-3-acetate biosynthesis III (bacteria)
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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