Formation of auxin from tryptophan through action of polyphenols.

Plant preparations that convert tryptophan to in(loleacetic acid (IAA) characteristically have low reaction yields. Since such preparations sometimes also contain IAA-oxidase activity, inhibition of the oxidase might raise the yields of IAA. Accordingly, polyphenolic inhibitors (1, 11, 19, 33, 40) were added to incubation mixtures containing tryptophan and a seedling enzyme preparation that was able to convert tryptophan to IAA. More than tenfold increases in auxin yield resulted. However, the presence of auxin in enzymeless controls, plus experiments on the recovery of added IAA, indlicated that the enhancements observed might be caused by a polyphenolic oxidation of tryptophan to IAA. We shall present evidence that the sequence