%0 Journal Article
%T Nucleoside Phosphorylases make N7-xanthosine.
%A Westarp S
%A Brandt F
%A Neumair L
%A Betz C
%A Dagane A
%A Kemper S
%A Jacob CR
%A Neubauer P
%A Kurreck A
%A Kaspar F
%J Nat Commun
%V 15
%N 1
%D 2024 Apr 29
%M 38684649
%F 17.694
%R 10.1038/s41467-024-47287-4
%X Modern, highly evolved nucleoside-processing enzymes are known to exhibit perfect regioselectivity over the glycosylation of purine nucleobases at N9. We herein report an exception to this paradigm. Wild-type nucleoside phosphorylases also furnish N7-xanthosine, a "non-native" ribosylation regioisomer of xanthosine. This unusual nucleoside possesses several atypical physicochemical properties such as redshifted absorption spectra, a high equilibrium constant of phosphorolysis and low acidity. Ultimately, the biosynthesis of this previously unknown natural product illustrates how even highly evolved, essential enzymes from primary metabolism are imperfect catalysts.