Biosynthesis of the tunicamycin antibiotics proceeds via unique exo-glycal intermediates.
The tunicamycins are archetypal nucleoside antibiotics targeting bacterial peptidoglycan biosynthesis and eukaryotic protein N-glycosylation. Understanding the biosynthesis of their unusual carbon framework may lead to variants with improved selectivity. Here, we demonstrate in vitro recapitulation of key sugar-manipulating enzymes from this pathway. TunA is found to exhibit unusual regioselectivity in the reduction of a key α,β-unsaturated ketone. The product of this reaction is shown to be the preferred substrate for TunF--an epimerase that converts the glucose derivative to a galactose. In Streptomyces strains in which another gene (tunB) is deleted, the biosynthesis is shown to stall at this exo-glycal product. These investigations confirm the combined TunA/F activity and delineate the ordering of events in the metabolic pathway. This is the first time these surprising exo-glycal intermediates have been seen in biology. They suggest that construction of the aminodialdose core of tunicamycin exploits their enol ether motif in a mode of C-C bond formation not previously observed in nature, to create an 11-carbon chain.
Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK.
Filip J
FJ
Wyszynski
Seung Seo
SS
Lee
Tomoaki
T
Yabe
Hua
H
Wang
Juan Pablo
JP
Gomez-Escribano
Mervyn J
MJ
Bibb
Soo Jae
SJ
Lee
Gideon J
GJ
Davies
Benjamin G
BG
Davis
D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D055162:Biocatalysis; D002238:Carbohydrate Epimerases / Q000737:chemistry / Q000378:metabolism; D019295:Computational Biology; D006836:Hydro-Lyases / Q000737:chemistry / Q000378:metabolism; D007659:Ketones / Q000737:chemistry / Q000378:metabolism; D005810:Multigene Family; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000201:enzymology; D013237:Stereoisomerism; D013379:Substrate Specificity; D014415:Tunicamycin / Q000096:biosynthesis* / Q000737:chemistry
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D007659:Ketones; D014415:Tunicamycin; D006836:Hydro-Lyases; C441972:wbpM protein, Pseudomonas aeruginosa; D002238:Carbohydrate Epimerases; C023223:UDP-N-acetylglucosamine 4-epimerase