PDF(Pubmed)
Abstract：
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.
摘要：
现代,已知高度进化的核苷加工酶对N9处嘌呤核碱基的糖基化表现出完美的区域选择性。我们在此报告了这一范式的一个例外。野生型核苷磷酸化酶还提供N7-黄嘌呤，黄苷的“非天然核糖基化区域异构体”。这种不寻常的核苷具有几种非典型的物理化学性质，如红移吸收光谱，磷解和低酸度的高平衡常数。最终,这种以前未知的天然产物的生物合成说明了甚至是高度进化的，来自初级代谢的必需酶是不完美的催化剂。
