Identifying the Biosynthetic Gene Cluster for Triacsins with anN-hydroxytriazene Moiety

Abstract

Triacsins are a family of natural products containing an N-hydroxytriazene moiety not found in any other known secondary metabolites. Though many studies have examined the biological activity of triacsins in lipid metabolism, the biosynthesis of triacsins has remained unknown. Here, we report the identification of the triacsin biosynthetic gene cluster in Streptomyces aureofaciens ATCC 31442. Bioinformatic analysis of the gene cluster led to the discovery of the tacrolimus producer Streptomyces tsukubaensis NRRL 18488 as a new triacsin producer. In addition to targeted gene disruption to identify necessary genes for triacsin production, stable isotope feeding was performed in vivo to advance the understanding of N-hydroxytriazene biosynthesis.

Synthetic and biosynthetic routes to nitrogen–nitrogen bonds

“…Finally, they observed highly related gene clusters in Salinispora arenicola CNS-205 and Streptomyces tsukubaenis NRRL 18488, the latter of which was also proved to be a triacsin producer. 260 Very recently, through extensive mutagenesis and in vitro biochemical studies, Zhang and coworkers elucidated the detailed biosynthetic pathway of triacsins, including the timing and mechanisms of two discontinuous N-N bond formations to construct the N-hydroxytriazene moiety. 116 HAA 114 was confirmed to be a key intermediate for triacsins biosynthesis, consistent with the previous bioinformatic analysis and glycine feeding results.…”

Nitric oxide as a source for bacterial triazole biosynthesis

“…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.…”

New frontiers in flavin-dependent monooxygenases

“…The NMOs, FzmM and its analog CreE convert aspartic acid to nitrosuccinate via double hydroxylation. Nitrosuccinate is subsequently converted to nitrous acid and fumarate by FzmL or CreD [9,68,69]. Nitrous acid is the N-donor for the formation of the N-N bond in the biosynthetic pathways of fosfazinomycin and cremeomycin.…”