Several nucleoside natural product antibiotics from Streptomyces sp. and actinomycetes have recently been shown to target bacterial peptidoglycan cell wall biosynthesis by inhibiting the bacterial translocase I (MraY). The biosynthetic gene clusters for A-90289, liposidomycins and caprazamycins revealed a protein with sequence similarity to proteins annotated as α-KG:taurine dioxygenases (TauD). This enzyme (LipL) is a mononuclear, non-heme, Fe(II) dependent α-KG:UMP dioxygenase responsible for the net dephosphorylation and two electron oxidation of uridine monophosphate (UMP) to uridine-5'-aldehyde. The postulated radical mechanism involving the formation of an unstable hydroxylated intermediate is investigated via the characterization of a key product obtained from the reaction of LipL (and its homolog Cpr19) with a synthetically modified surrogate substrate where the bridging phosphoester oxygen in UMP is replaced with a 5' C-P bond. We also exploit the broad substrate specificity of Cpr19 as a means of conducting precursor-directing biosynthesis with a view to generating interesting novel intermediates in the biosynthetic pathway with potential improved therapeutic values. The development of 18 O2, H2
17 O and elemental sulfur labeled UMP is also discussed as an alternate strategy to tracking the fate of the eliminated phosphate.
