Enzymatically generated electronically excited molecules induce transformation of 4-thiouridine to uridine

Oxidation of 4-thiouridine-5'-monophosphate in t-RNA, from E. coli, by singlet oxygen generated via self-sensitization, photosensitization or by energy transfer from bioenergized systems yields uridine-5'-monophosphate. Studies with absorption, fluorescence and circular dichroism techniques showed similar interactions between singlet oxygen and the nucleotide in t-RNA generated by either optical or enzymatic systems. Protection by histidine and an enhancement of the photodegradation in the presence of D2O corroborates the important role of singlet oxygen in these processes.