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A. Müller, E.W. Weiler

IAA-Synthase, an Enzyme Complex from Arabidopsis thaliana Catalyzing the Formation of Indole-3-Acetic Acid from (S)-Tryptophan

An enzyme complex was isolated from Arabidopsis thaliana that catalyzes the entire pathway of biosynthesis of the major plant growth hormone, indole-3-acetic acid (IAA), from (S)-tryptophan. The 160–180 kDa, soluble complex catalyzes a strictly O₂-dependent reaction which requires no further added factors and is stereospecific for the substrate (S)-tryptophan (app. K_m = 120?M). H₂ ¹⁸O labeling proved that both oxygen atoms of IAA were delivered via H₂O. This, as well as immunological evidence for the presence of a nitrilase-like protein in the complex, suggests the reaction to proceed via the intermediate indole-3-acetonitrile. IAA-synthase forms a tight metabolite channel committed to IAA production and occurs in shoots, roots and cell cultures of A. thaliana.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 381, 09/2000
Pages: 679 - 686

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