The in dole-3-acetic acid oxidase of Lupinus luteus L. II. A quantitative comparison of the activity of this enzyme in root nodules and roots

The activity was determined of the various enzyme fractions obtained during ammonium sulphate precipitation and gel filtration of the lAA-oxidase present in root nodules and roots of Lupinus luleus L. Comparison of these activities on a protein basis showed that IAA degradation was lower in root nodules than in roots. Several indications were obtained that phenols were present in all of the enzyme fractions and had an inhibitory effect on the enzyme activity. The possible role of phenols in the regulation of lAA-oxidase activity in lupine is discussed. Rhizobium lupini was isolated from the root nodules, and cell-free enzyme preparations of these bacteria oxidized IAA. The results obtained with cell-free enzyme preparations of bacteroids did not, however, prove conclusively that the bacteroids have this activity.