Summary: subsequent O-to-N rearrangement via 1,4-addition
of the serine nitrogen to the activated cyclohex-
enimine core (Fig. 3B). We favor this pathway, as
it is consistent with the poor electrophilicity of
mycosporine glycine (24); an alternative mecha-
nism for Ava_3855 involving a direct condensa-
tion is detailed in scheme S3.
The in vitro characterization of Ava_3856
and Ava_3855 reveals two distinct, yet comple-
mentary, mechanisms of ATP-dependent enzymatic
imine formation that differ from conventional
chemical methods and biochemical mechanisms.
These enzymes have evolved from peptide bond­
forming catalysts in distinct ways: ATP-grasp
homolog Ava_3856 generates a new type of elec-
trophile using vinylogous acid activation, and
NRPS-like enzyme Ava_3855 likely employs an
unusual release mechanism. The recruitment of
ATP-dependent peptide bond­forming enzymes
in this manner is so far unprecedented in natural

Source: Arnold, Frances H. - Division of Chemistry and Chemical Engineering, California Institute of Technology
Elowitz, Michael - Division of Biology, California Institute of Technology
van Oudenaarden, Alexander - Department of Physics, Massachusetts Institute of Technology (MIT)

Collections: Biology and Medicine; Chemistry; Physics