Identification and Cloning of the Gene Involved in the Final Step of Chlortetracycline Biosynthesis inStreptomyces aureofaciens

Physiology, Biochemistry, and Applications of F420- and Fo-Dependent Redox Reactions

“…Thereafter, the nonribosomal peptide synthase F 420 :␥-L-glutamyl ligase (CofE/FbiB) catalyzes the GTP-dependent addition of an oligoglutamate tail (118,(120)(121)(122). L-Glutamate residues are added via ␥-linkages to F 420 -0 (F 420 -0 ϩ glutamate ϩ GTP ¡ F 420 -1 ϩ GDP ϩ P i ) and glutamated derivatives thereof (F 420 -n ϩ glutamate ϩ GTP ¡ F 420 -n ϩ 1 ϩ GDP ϩ P i ) in a sequential manner.…”

“…As far back as 1960, McCormick et al isolated a hydride-transferring cofactor mediating tetracycline biosynthesis (24,(381)(382)(383), now known to be F 420 (29,122,384). A combination of genetic and biochemical studies have since shown that an F 420 H 2 -dependent reductase (OxyR) catalyzes the final step of oxytetracycline biosynthesis (385), namely, reduction of the C-5aϭC-11a double bond of dehydrooxytetracycline ( Fig.…”

“…While it has been proposed that FDOR-A proteins are F 420 H 2 -dependent menaquinone reductases (32), to date, activity has been observed only with nonphysiological quinones (e.g., menadione), rather than with menaquinone (30,32); hence, it is unclear whether these enzymes have primarily evolved to input electrons into the respiratory chain or instead detoxify exogenous redox cycling agents (section 4.1.1). Finally, it was recently shown that the F 420 H 2 -dependent step in the biosynthesis of antibiotics of the tetracycline, oxotetracycline, and chlortetracycline classes (122,381,382,384 420 -reducing glucose-6-phosphate dehydrogenase (Fgd), and F 420 -reducing hydroxymycolic acid dehydrogenase (fHMAD). However, comparative genome analysis indicates that there are numerous other F 420 -dependent LLHTs in actinomycetes, the majority probably serving as reductases (37).…”

Oxytetracycline Biosynthesis

“…Nakano et al (74) identified a gene from Streptomyces aureofaciens that was shown to be responsible for this last step in the biosynthesis of CTC. This gene, encoding TchA, was mapped outside of the previously sequenced CTC gene cluster.…”

“…This gene, encoding TchA, was mapped outside of the previously sequenced CTC gene cluster. TchA requires 7,8-dedimethyl-8-hydroxy-5-deazariboflavin as a cofactor (74), which explains why mutants blocked in 7,8-dedimethyl-8-hydroxy-5-deazariboflavin biosynthesis, previously referred to as cosynthetic factor I, were also blocked in this final reduction step (31,75). In the oxy pathway, there is no clear enzyme candidate that may be associated with this step.…”