Synthetic Polyketide Enzymology: Platform for Biosynthesis
of Antimicrobial Polyketides
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Abstract
Synthetic
biology often employs enzymes in the biosynthesis of compounds for
purposeful function. Here, we define synthetic enzymology as the application
of enzymological principles in synthetic biology and describe its
use as an enabling platform in synthetic biology for the purposeful
production of compounds of biomedical and commercial importance. In
particular, we demonstrated the use of synthetic polyketide enzymology
as a means to develop lead polyketide based compounds for antimicrobial
therapeutics, as exemplified by the modular coupling of acid:CoA ligases
to type III polyketide synthases in the biosynthesis and development
of polyketide-based biochemicals. Using wild-type and rationally designed
mutants of a type III polyketide synthase isolated from Oryza sativa (OsPKS), we produced a chemically diverse
library of novel polyketides and identified two bioactive antimicrobials,
4-hydroxy-6-[(1<i>E</i>)-2-(4-hydroxyphenyl)ethenyl]-2<i>H</i>-pyran-2-one (bisnoryangonin) and 3,6,7-trihydroxy-2-(4-methoxybenzyl)-4<i>H</i>-1-benzopyran-4,5,8-trione (26OH), respectively, from a
screen against a collection of Gram-positive and Gram-negative bacteria.
The purification, crystallization, and structural resolution of recombinant
OsPKS at 1.93 Å resolution are also reported. Using the described
route of synthetic polyketide enzymology, a library of OsPKS mutants
was generated as an additional means to increase the diversity of
the polyketide product library. We expect the utility of synthetic
enzymology to be extended to other classes of biomolecules and translated
to various purposeful functions as the field of synthetic biology
progresses