Effects of Indol-3yl Acetic Acid on the Citrate-Condensing Reaction by Preparations of Root and Shoot Tissue

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Abstract
Preparations of citrate condensing enzyme (citrate oxaloacetate-lyase (CoA-acetylating) E. C. 4. 1. 3. 7) from root and shoot tissue of 5½-day-old bean seedlings (Phaseolus vulgaris L., var. Burpee's Stringless Greenpod) had different activities, expressed as reaction rate per unit of fresh tissue. Activity per mg protein was increased when protein concentrations of the preparations were reduced by dilution. Addition of indol-3yl acetic acid (IAA) enhanced activity of both root and shoot preparations. The effect was optimal at a concentration of 1.25×10-4 M and the enzyme was inhibited at 1.25×10-3 M. Enhanement was greater in root than in shoot preparations and in mixtures of equal amounts of each prepartion activity was intermediate between those of the separte enzymes in absence of IAA but in its presence approached that of the shoot preparation. Apparent citrate synthesis in vivi was increased in shoots by application of IAA but there was no such effect in roots.