Efficient synthesis of 2’-deoxyguanosine in one-pot cascade by employing an engineered purine nucleoside phosphorylase from Brevibacterium acetylicum

2’-deoxyguanosine is a key medicinal intermediate that could be used to synthesize anti-cancer drug and biomarker in type 2 diabetes. In this study, an enzymatic cascade using thymidine phosphorylase from Escherichia coli ( Ec TP) and purine nucleoside phosphorylase from Brevibacterium acetylicum ( Ba PNP) in a one-pot whole cell catalysis was proposed for the efficient synthesis of 2’-deoxyguanosine. Ba PNP was semi-rationally designed to improve its activity, yielding the best triple variant Ba PNP-Mu3 (E57A/T189S/L243I), with a 5.6-fold higher production of 2’-deoxyguanosine than that of wild-type Ba PNP ( Ba PNP-Mu0). Molecular dynamics simulation revealed that the engineering of Ba PNP-Mu3 resulted in a larger and more flexible substrate entrance channel, which might contribute to its catalytic efficiency. Furthermore, by coordinating the expression of Ba PNP-Mu3 and Ec TP, a robust whole cell catalyst W05 was created, capable of producing 14.8 mM 2’-deoxyguanosine (74.0% conversion rate) with a high time-space yield (1.32 g/L/h) and therefore being very competitive for industrial applications.