-Ribosyltransferase From : A Novel Halotolerant and Thermostable Biocatalyst for the Synthesis of Purine Ribonucleoside Analogs.

Nucleoside-2'-deoxyribosyl-transferases (NDTs) catalyze a transglycosylation reaction consisting of the exchange of the 2'-deoxyribose moiety between a purine and/or pyrimidine nucleoside and a purine and/or pyrimidine base. Because NDTs are highly specific for 2'-deoxyribonucleosides they generally display poor activity on modified C2' and C3' nucleosides and this limitation hampers their applicability as biocatalysts for the synthesis of modified nucleosides. We now report the production and purification of a novel NDT from that is endowed with native ribosyltransferase activity and hence it is more properly classified as an -ribosyltransferase (NRT). Biophysical and biochemical characterization revealed that NRT is a homotetramer that displays maximum activity at 80°C and pH 6 and shows remarkably high stability at high temperatures (60-80°C). In addition, the activity of NRT was found to increase up to 2-fold in 4 M NaCl aqueous solution and to be retained in the presence of several water-miscible organic solvents. For completeness, and as a proof of concept for possible industrial applications, this thermophilic and halotolerant biocatalyst was successfully employed in the synthesis of different purine ribonucleoside analogs.