Nucleoside phosphorylases and deoxyribonucleoside kinases: the green side of nucleic acid chemistry

Biocatalysis has become nowadays an important tool in synthetic organic chemistry. Biotransformations are chemo-, regio-, and stereoselective, occur under mild reaction conditions and are characterized by a reduced use of toxic reagents/solvents. One of the areas where biocatalyzed reactions have clearly shown their potential is nucleic acid chemistry. Enzymes of nucleic acid metabolism such as nucleoside phosphorylases (NPs, EC 2.4.2) and deoxyribonucleoside kinases (dNKs, EC 2.7.1) can be conveniently used as biocatalysts in the synthesis of nucleoside and nucleotide analogues. NPs catalyze the reversible cleavage of the glycosidic bond of (deoxy)ribonucleosides in the presence of inorganic orthophosphate to generate the nucleobase and alpha-D- (deoxy)ribose-1-phosphate. If a second nucleobase is added to the reaction, the formation of a new nucleoside can result (transglycosylation). dNKs catalyze the regioselective transfer of a phosphate group from ATP to a nucleoside to give the corresponding nucleoside 5’-monophosphate. However, the bottleneck in the use of enzymes as biocatalysts is often their instability under experimental conditions, their cost and solubility in the reaction medium. These issues can be frequently overcome by immobilizing the enzyme on a solid support. Substrate specificity, immobilization and some synthetic applications of selected NPs and dNKs will be described.