Characterization of Two Aromatic Amino Acid Aminotransferases and Production of Indoleacetic Acid in Azospirillum Strains

Sunnnary-Experiments were made to quantify indole-3-acetic acid (IAA) excreted by different wild type strains of Azospirilhun spp. The microorganisms produce IAA, during the late stationary growth phase and show a significant increase in IAA production when tryptophan is present in the medium. Under these conditions with the A. brusilense strain UAP 14, we observed two aromatic amino acid aminotransferases. Their enzymatic activity and electrophoretic mobility under non-denaturating conditions were characterized using cell-free extracts. Biochemical studies showed that these two enzymes can be distinguished by their electrophoretic mobilities. These enzymes are constitutively produced and they are not repressed by tyrosine or by tyrosine plus phenlylalanine.