Induction And Characterization of an Indole-3-acetyl-L-alanine Hydrolase From Arthrobacter Ilicis

Abstract

Indole-3-acetic acid (IAA)-amino acid amide conjugates have been found to be present in many plants, and they are proposed to function in the regulation of plant IAA metabolism in a variety of ways. IAA-amino acid conjugate hydrolase activities, and the genes that encode them, are therefore potentially important tools for modification of IAA metabolism, both for agronomic reasons as well as for determination of the mechanisms of IAA regulation. We have developed a simple and economical method to induce IAA-amino acid conjugate hydrolases in bacteria with N-acetyl-L-amino acids. Using this method, we identified four bacterial strains that can be induced to produce IAA-Ala hydrolases: Arthrobacter ureafaciens C-10, Arthrobacter ureafaciens C-50, Arthrobacter ilicis D-50, and Cellulomonas fimi D-100. The enzyme kinetics and the biochemical characteristics of IAA-Ala hydrolase from one specific bacterium, Arthrobacter ilicis D-50, have been determined. The enzyme has a unique substrate specificity for IAA-amino acid conjugates compared to a bacterial IAA-Asp hydrolase previously characterized.