STEREOCHEMISTRY OF DTDP-GLUCOSE OXIDOREDUCTASE REACTION

  • 1 January 1977
    • journal article
    • research article
    • Vol. 252  (22) , 8113-8117
Abstract
The stereochemical course of the dTDP-glucose oxidoreductase (EC 4.2.1.46) reaction was studied using enzyme partially purified from Escherichia coli and dTDP-(6R)-and (6S)-[4-2H, 6-3H]glucose as substrate. The latter was prepared enzymatically by reduction of (3R)- and (3S)-3-P[phosphate]-[3-3H]glycerate to the 1-deuterated 3-P-glyceraldehyde with (4S)-[4-2H]NADH, followed first by conversion to glucose-1-P with the glycolytic enzymes, and then by transformation into the dTDP derivative. The stereospecifically labeled dTDP-glucose samples were mixed with nonlabeled carrier material and converted to dTDP-4-keto-6-deoxyglucose, which contained a chiral methyl group as shown by chirality analysis of the acetic acid resulting from Khun-Roth oxidation of the sugar nucleotide. The H transfer from C4 to C6 is intramolecular and show that the migrating H replaces the 6-hydroxyl group with inversion of configuration. Assuming that the H transfer, since it is intramolecular, must be suprafacial, the elimination of water from C5 and C6 is formally syn, but the reduction of the resulting .DELTA.5,6-double bond formally involves an anti addition of H+ and H-.