The Biosynthetic Gene Cluster of Pyrazomycin—A C‐Nucleoside Antibiotic with a Rare Pyrazole Moiety

Abstract

Pyrazomycin is a rare C‐nucleoside antibiotic containing a naturally occurring pyrazole ring, the biosynthetic origin of which has remained obscure for decades. In this study we report the identification of the gene cluster responsible for pyrazomycin biosynthesis in Streptomyces candidus NRRL 3601, revealing that the StrR‐family regulator PyrR is the cluster‐situated transcriptional activator governing pyrazomycin biosynthesis. Furthermore, our results from in vivo reconstitution and stable‐isotope feeding experiments provide support for the hypothesis that PyrN is a new nitrogen–nitrogen bond‐forming enzyme that catalyzes the linkage of the ϵ‐NH2 nitrogen atom of l‐N6‐OH‐lysine and the α‐NH2 nitrogen atom of l‐glutamic acid. This study lays the foundation for further genetic and biochemical characterization of pyrazomycin pathway enzymes involved in constructing the characteristic pyrazole ring.

Uncovering the chemistry of C–C bond formation inC-nucleoside biosynthesis: crystal structure of aC-glycoside synthase/PRPP complex

“… 5 , 6 With the exception of pseudouridine synthase, 7 , 8 relatively little is known about the structures and catalytic mechanisms of enzymes that form C -ribosides and C -glycosides. 9 , 10 Recent work identifying the biosynthetic gene clusters for formycin A 1 , 11 – 13 pyrazomycin 2 (also known as pyrazofurin) 14 , 15 and showdomycin 3 16 ( Fig. 1a ) has laid the foundation for obtaining an enhanced understanding of two new enzymes (ForT and PyfQ), both of which catalyse C–C bond-forming steps in C -nucleotide biosynthesis.…”

Nitric oxide as a source for bacterial triazole biosynthesis

“…To connect two nitrogen atoms together, nature has devised different strategies. The most frequently used precursors for N-N bond formation are hydroxylamines (such as L-N 5 -OH-Ornthine in piperazate pathway 9 , N-isobutylhydrdoxylamine in valanimycin pathway 37 , and L-N 6 -OH-lysine in the pathways of s56-p1 14 , pyrazomycin 16 and formycin 17,38 ) and nitric acid, which derives from the α-amine of L-aspartic acid by the enzyme pair CreE and CreD 10 . The flavin monooxygenase CreE and nitrosuccinate lyase CreD were first characterized in the cremeomycin pathway, and their homologs were subsequently identified in the pathways of fosfazinomycin, and kinamycin, triacsins and alanosine 15,[21][22][23] .…”

“…While the biosynthetic routes to natural products containing a N-N bond have received great interest and are starting to be revealed, how a triazole ring is assembled in nature remains unknown [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] . Elucidation of its biosynthetic mechanism could likely be helpful to the design of synthetic biology approaches for producing triazoles.…”

Natural and Biomimetic Antitumor Pyrazoles, A Perspective

“…Pyrazofurin (3), depicted in Figure 5, is a naturally occurring nucleoside analogue produced by Streptomyces candidus. It has been known for decades, but only very recently has its biosynthesis begun to be elucidated, with researchers unveiling the involvement of PyrN, a new enzyme capable of forming the N-N bond [29]. Since its discovery in 1969, pyrazofurin has been the target of much interest due to its antimicrobial, antiviral, and antitumor properties, and for this reason a patent covering its bioindustrial production process was filed on the same year (and granted in 1974) [30].…”