TY - JOUR
T1 - Definition of the common and divergent steps in carbapenem β-lactam antibiotic biosynthesis
AU - Bodner, Micah J.
AU - Li, Rongfeng
AU - Phelan, Ryan M.
AU - Freeman, Michael F.
AU - Moshos, Kristos A.
AU - Lloyd, Evan P.
AU - Townsend, Craig A.
PY - 2011/9/19
Y1 - 2011/9/19
N2 - Approximately 50 naturally occurring carbapenem β-lactam antibiotics are known. All but one of these have been isolated from Streptomyces species and are disubstituted structural variants of a simple core that is synthesized by Pectobacterium carotovorum (Erwinia carotovora), a phylogenetically distant plant pathogen. While the biosynthesis of the simple carbapenem, (5R)-carbapen-2-em-3-carboxylic acid, is impressively efficient requiring only three enzymes, CarA, CarB and CarC, the formation of thienamycin, one of the former group of metabolites from Streptomyces, is markedly more complex. Despite their phylogenetic separation, bioinformatic analysis of the encoding gene clusters suggests that the two pathways could be related. Here we demonstrate with gene swapping, stereochemical and kinetics experiments that CarB and CarA and their S. cattleya orthologues, ThnE and ThnM, respectively, are functionally and stereochemically equivalent, although their catalytic efficiencies differ. The biosynthetic pathways, therefore, to thienamycin, and likely to the other disubstituted carbapenems, and to the simplest carbapenem, (5R)-carbapen-2-em-3-carboxylic acid, are initiated in the same manner, but share only two common steps before diverging.
AB - Approximately 50 naturally occurring carbapenem β-lactam antibiotics are known. All but one of these have been isolated from Streptomyces species and are disubstituted structural variants of a simple core that is synthesized by Pectobacterium carotovorum (Erwinia carotovora), a phylogenetically distant plant pathogen. While the biosynthesis of the simple carbapenem, (5R)-carbapen-2-em-3-carboxylic acid, is impressively efficient requiring only three enzymes, CarA, CarB and CarC, the formation of thienamycin, one of the former group of metabolites from Streptomyces, is markedly more complex. Despite their phylogenetic separation, bioinformatic analysis of the encoding gene clusters suggests that the two pathways could be related. Here we demonstrate with gene swapping, stereochemical and kinetics experiments that CarB and CarA and their S. cattleya orthologues, ThnE and ThnM, respectively, are functionally and stereochemically equivalent, although their catalytic efficiencies differ. The biosynthetic pathways, therefore, to thienamycin, and likely to the other disubstituted carbapenems, and to the simplest carbapenem, (5R)-carbapen-2-em-3-carboxylic acid, are initiated in the same manner, but share only two common steps before diverging.
KW - Beta-lactam antibiotics
KW - Biosynthesis
KW - Carbapenems
KW - Enzyme catalysis
KW - Thienamycin
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U2 - 10.1002/cbic.201100366
DO - 10.1002/cbic.201100366
M3 - Article
C2 - 21913298
AN - SCOPUS:80052711348
SN - 1439-4227
VL - 12
SP - 2159
EP - 2165
JO - ChemBioChem
JF - ChemBioChem
IS - 14
ER -