Enzymatic synthesis of nucleosides by nucleoside phosphorylase co-expressed in Escherichia coli

Nucleoside phosphorylase is an important enzyme involved in the biosynthesis of nucleosides.In this study,purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase were co-expressed in Escherichia coli and the intact cells were used as a catalyst for the biosynthesis of nucleosides.For protein induction,lactose was used in place of isopropylβ-D-1-thiogalactopyranoside(IPTG) .When the concentration of lactose was above 0.5 mmol/L,the ability to induce protein expression was similar to that of IPTG.We determined that the reaction conditions of four bacterial strains co-expressing these genes(TUD,TAD,DUD,and DAD) were similar for the biosyntheses of 2,6-diaminopurine nucleoside and 2,6-diaminopurine deoxynucleoside.When the substrate concentration was 30 mmol/L and 0.5%of the recombinant bacterial cell volume was used as the catalyst(pH 7.5) ,a greater than 90%conversion yield was reached after a 2-h incubation at 50°C.In addition,several other nucleosides and nucleoside derivatives were efficiently synthesized using bacterial strains co-expressing these recombinant enzymes.

Nucleoside phosphorylase is an important enzyme involved in the biosynthesis of nucleosides. In this study, purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase were co-expressed in Escherichia coli and the intact cells were used as a catalyst for the biosynthesis of nucleosides. For protein induction, lactose was used in place of isopropyl β-D-l-thiogalactopyranoside （IPTG）. When the concentration of lactose was above 0.5 mmol/L, the ability to induce protein expression was similar to that of IPTG. We determined that the reaction conditions of four bacterial strains co-expressing these genes （TUD, TAD, DUD, and DAD） were similar for the biosyntheses of 2,6-diaminopurine nucleoside and 2,6-diaminopurine deoxynucleoside. When the substrate concentration was 30 mmol/L and 0.5% of the recombinant bacterial cell volume was used as the catalyst （pH 7.5）, a greater than 90% conversion yield was reached after a 2-h incubation at 50℃. In addition, several other nucleosides and nucleoside derivatives were efficiently synthesized using bacterial strains co-expressing these recombinant enzymes.