N -Ribosyltransferase From Archaeoglobus veneficus : 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 fromArchaeoglobus veneficusthat is endowed with native ribosyltransferase activity and hence it is more properly classified as anN-ribosyltransferase (AvNRT). Biophysical and biochemical characterization revealed thatAvNRT is a homotetramer that displays maximum activity at 80 degrees C and pH 6 and shows remarkably high stability at high temperatures (60-80 degrees C). In addition, the activity ofAvNRT 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.