3-Deoxy-D-arabino-heptulosonic Acid 7-Phosphate Synthase in Sweet Potato Roots*

Publisher Website
Google Scholar
Abstract
1. Extracts of sweet potato roots were shown to have the activity of DAHP synthase [EC 4.1.2.15], which catalyzes the conversion of E4P and PEP to DAHP. The product formed by action of the enzyme was identified as DAHP by the absorption spectrum of the derivative formed by periodate oxidation and TBA treatment. The product of the reaction was also identified by paper chromatography of the reaction mixture. 2. Mg++ at 1 mM concentration increased the rate of DAHP formation by 65 to 120%. K+ (50 mM) had no effect. Addition of reduced glutathione (1 to 3 mM) to either the enzyme extraction medium or reaction mixture was not effective. 3. The root tissues were sliced and placed at 28–29°C, and DAHP synthase activity was analyzed at 24-hour intervals for 4 days. DAHP synthase activity was found to remain relatively constant without marked change due to slicing. 4. Several plants were assayed for DAHP synthase activity. Of the plants tested, the activity was detected only in Trifolium repens. Mg++ (5 mM) was required for maximum activity.