Conversion of Tryptophan-2-C14 to Indoleacetic Acid by Watermelon Tissue Slices

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Abstract
Slices of young watermelons (7-10 days post-pollination) were placed in buffered solution containing tryptophan-2-C14 and allowed to incubate for 20 hours. The tissue was macerated, boiled to inactivate the enzymes and precipitate the protein, the brei was centrifuged, and the supernatant partitioned into acidic, basic, neutral and residual aqueous fractions for chromatography. Chromatog-raphy was on Whatman 3MM paper in isopropanol; ammonia: water in the ratio of 8:1:1 (v/v) for the one-dimensional separations and in isopropanol acetic acid: water (6 ml glacial acetic acid/100 ml 80% isopropanol) for the first direction and the above ammonia solvent in the second direction for the two dimensional separations. A number of indole compounds were found which showed radioactivity, among which were indolepyruvic acid, indoleacetonitrile, 5-OH-tryptophan, tryptamine, indoleacetic acid, and other compounds thought to be degradation products of indolepyruvic and indoleacetic acids. The evidence, although not compelling, indicates that indolepyruvic is the principal intermediate for indoleacetic acid synthesis in watermelon.