Characterization of NucPNP and NucV involved in the early steps of nucleocidin biosynthesis in <i>Streptomyces calvus</i>

Abstract

Nucleocidin 1 produced by <i>Streptomyces calvus</i> is one of five characterized natural products containing fluorine. It was discovered in 1956, but its biosynthesis is not yet completely resolved. Recently, the biosynthetic gene cluster of 1 was identified. The <i>nucPNP</i> gene, which was initially annotated as <i>orf206</i> and encodes a putative purine nucleoside phosphorylase, is essential for nucleocidin production. In this study, we performed <i>in vitro</i> assays and showed NucPNP produced adenine 3 from methylthioadenosine (MTA) 2 and adenosine 4. We also showed the downstream enzyme, NucV annotated as adenine phosphoribosyltransferase (APRT), catalyzes AMP formation from adenine 3 and 5-phospho-α-d-ribose-1-diphosphate (PRPP) 5. However, the catalytic efficiency of NucV was much slower than its homolog <i>Sc</i>APRT involved in the biosynthesis of canonical purine nucleoside in the same strain. These results provide new insights in nucleocidin biosynthesis and could guide future research on organofluorine formation.