Cloning and expression of recombinant purine nucleoside phosphorylase in the methylotrophic yeast Pichia pastoris

Purine nucleoside phosphorylase (PNP) is an enzyme involved in biosynthetic pathway of purine nucleosides. Purine nucleoside phosphorylase catalyzes the cleavage of the glycosidic bond of ribo- or deoxyribonucleosides to form the purine base and deoxyribose- or ribose-1-phosphate. The reversible reaction catalyzed by recombinant PNP of E. coli (EcPNP) has been successfully used for the synthesis of nucleoside analogues. The aim of this study was to clone and expression of recombinant PNP in Pichia pastoris. For expression of recombinant EcPNP in Pichia pastoris, a new recombinant plasmid DNA pPICZαA-PNP (4256 bp) containing the deoD gene (720 bp) amplified from E. coli strain RKMUz-221 has been cloned. The substrate specificity of the recombinant EcPNP expressed in yeast cells was studied by hydrolysis of inosine (9-beta-D-ribofuranosylhypoxanthine) to hypoxanthine and 2-deoxy-β-D-ribofuranosyl. The fraction containing the obtained recombinant EcPNP (≈28 kDa, as determined by SDS-PAGE) demonstrates significant hydrolytic activity, resulting in up to a 51% hydrolysis of inosine within a 5 h timeframe. These findings suggest that the recombinant enzyme holds a promise for applications in enzymatic transglycosylation of purine-type nucleosides.