Mechanism and stereochemistry of 5-dehydroquinate synthetase.
3-Deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) labeled at C-7 randomly or stereospecifically with tritium and at C-1 with (14)C was converted enzymically to 5-dehydroquinate. Tritium of all three substrates was completely retained in 5-dehydroquinate, in accord with formation of a non-ketonizing 6,7-enol intermediate. The 5-dehydroquinates were dehydrated to 5-dehydroshikimate by 5-dehydroquinate dehydratase, which is known to catalyze a cis-elimination. Only 5-dehydroquinate derived from [7-(3)H](7R)-DAHP lost its tritium in this dehydration, indicating that the configuration at C-7 was inverted in the conversion of DAHP to 5-dehydroquinate.
D002247:Carbon Isotopes; D055598:Chemical Phenomena; D002621:Chemistry; D003509:Cyclohexanecarboxylic Acids; D006836:Hydro-Lyases; D008025:Ligases; D010710:Phosphates; D011801:Quinic Acid; D012765:Shikimic Acid; D013237:Stereoisomerism; D014316:Tritium
D002247:Carbon Isotopes; D003509:Cyclohexanecarboxylic Acids; D010710:Phosphates; D011801:Quinic Acid; D014316:Tritium; D012765:Shikimic Acid; D006836:Hydro-Lyases; D008025:Ligases