Mechanistic Studies on a non-heme, Fe(II) dependent α-ketoglutarate:UMP dioxygenase that initiates the biosynthesis of high-carbon sugar nucleoside antibiotics

Several nucleoside antibiotics have been discovered the past decade by using an activity-based screen to identify inhibitors of bacterial translocase I (UDP-N-acetylmuramic acid-pentapeptide:undecaprenyl phosphate transferase), an essential enzyme involved in the biosynthesis of peptidoglycan cell wall. Two of the four structural classes of nucleoside antibiotics, the lipopeptidyl nucleosides represented by A-90289s, caprazamycins and muraminomicins and the capuramycins share a uracil-containing nucleoside component that is modified to generate a high-carbon riboside (C7 for the lipopeptidyl nucleosides and C6 for the capuramycins). In both nucleoside classes, a non-heme, Fe(II)-dependent a-ketoglutarate:UMP dioxygenase initiates the biosynthesis by catalyzing an unprecedented reaction: the net dephosphorylation and two electron oxidation of uridine monophosphate (UMP) to uridine-5’-aldehyde. We will present studies aimed at defining the chemical mechanism of this new group of dioxgyenases, including our strategy of perturbing the reaction kinetics by using substrate analogues and site-directed mutagenesis. Additionally, progress toward delineating the remaining steps in transforming the canonical nucleoside into a potent antibiotic will be presented.