| Abstract: | Dehydroquinate synthase, the enzyme which catalyzes the conversion of 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) to 5-dehydroquinate, has been purified from Bacillus subtilis in association with chorismate synthase and NADPH-dependent flavin reductase. The enzyme was only active when associated with chorismate synthase, whereas the flavin reductase could be separated from the complex with retention of dehydroquinate synthase activity. The enzyme requires NAD and either Co2+ or Mn2+ for maximal activity. The activity was completely inhibited by EDTA. The Km of the enzyme for DAHP, NAD, and Co2+ were estimated to be 1.3 X 10(-4), 5.5 X 10(-5), and 5.5 X 10(-5) M, respectively. Enzyme activity was completely inhibited by NADH and the inhibition was not reversed by the addition of NAD, NADPH and NADP were not inhibitory. The enzyme was unstable to heat and lost all activity at 55 degrees C. A protein fraction which did not adsorb to phosphocellulose was found to inhibit the enzyme. |
