De. Ehmann et al., Aminoacyl-SNACs as small-molecule substrates for the condensation domains of nonribosomal peptide synthetases, CHEM BIOL, 7(10), 2000, pp. 765-772
Background: Nonribosomal peptide synthetases (NRPSs) are large multidomain
proteins that catalyze the formation of a wide range of biologically active
natural products. These megasynthetases contain condensation (C) domains t
hat catalyze peptide bond formation and chain elongation. The natural subst
rates for C domains are biosynthetic intermediates that are covalently teth
ered to thiolation (T) domains within the synthetase by thioester linkages.
Characterizing C domain substrate specificity is important for the enginee
red biosynthesis of new compounds.
Results: We synthesized a series of aminoacyl-N-acetylcysteamine thioesters
(aminoacyl-SNACs) and show that they are small-molecule substrates for NRP
S C domains. Comparison of rates of peptide bond formation catalyzed by the
C domain from enterobactin synthetase with various aminoacyl-SNACs as down
stream (acceptor) substrates revealed high selectivity for the natural subs
trate analog L-Ser-SNAC. Comparing L- and D-Phe-SNACs as upstream (donor) s
ubstrates for the first C domain from tyrocidine synthetase revealed clear
D- versus L-selectivity,
Conclusions: Aminoacyl-SNACs are substrates for NRPS C domains and are usef
ul for characterizing the substrate specificity of C domain-catalyzed pepti
de bond formation.