Identification of enzymes involved in indole-3-acetic acid degradation

✍ Scribed by Marianne R. Olesen; Bjarne U. Jochimsen

• Publisher: Springer
• Year: 1996
• Tongue: English
• Weight: 441 KB
• Volume: 186
• Category: Article
• ISSN: 0032-079X
• DOI: 10.1007/bf00035068

✦ Synopsis

Strains of Bradyrhizobium japonicum with the ability to catabolize indole-3-acetic acid (IAA) and strains of B. japonicum, Rhizobium loti, and Rhizobium galegae, unable to catabolize IAA, were analyzed for enzymes involved in the pathway for IAA degradation. Two enzymes having isatin as substrate were detected. An isatin amidohydrolase catalyzing the hydrolysis of isatin into isatinic acid was found in some B. japonicum strains and in two Rhizobium species, R loti and R. galegae. The enzyme was inducible (4-5-fold) by its substrate, isatin, and the partially purified enzyme from R. loti showed an apparent KM of 11 #M for isatin. A NADPH-dependent isatin reductase was measured in extracts from a strain of B. japonicum lacking the isatin amidohydrolase. The structure of the reaction product, dioxindole was verified by NMR spectroscopy. Isatin reductase activity was also detected in extracts of dry pea seeds, and present in at least two isoforms. A low Ku of 10/d,/for isatin was found with a partially purified preparation of the pea enzyme. The presence of such an enzyme activity in pea indicates dioxindole and isatin as possible intermediates in IAA degradation in pea.