ABSTRACT
Natural metabolic diversity is generated through the evolution of novel function in enzymes
(neofunctionalization). Society uses this metabolic diversity to obtain many high-value chemicals, such
as microbial and plant-derived pharmaceuticals, but harnessing this chemistry relies on discovery of the
underlying biosynthetic machinery. While some biosynthetic enzymes are readily identifiable, there are
many metabolic reactions with no defined enzyme family, and this acts as a roadblock to elucidating
new metabolic pathways. My lab studies enzymes and chemical reactions from the natural world, with
a focus on identifying biosynthetic genes and pathways in medicinal plants. We are particularly
interested in finding new enzymes that expand the ‘catalog’ of known metabolic protein families.
Recently, we identified several α-carbonic anhydrase (CAH)-like proteins that have neofunctionalized
to catalyze novel scaffold-forming reactions in the biosynthesis of neuroactive plant compounds. While
these are the first CAH family proteins shown to act as biosynthetic enzymes, we predict that
neofunctionalized CAHs (neo-CAHs) have critical, undefined functions in metabolism more broadly.
Over the next five years, my lab will advance a fundamental understanding of neo-CAHs by
providing a mechanistic basis on their enzymatic function and by investigating the breadth and diversity
of neo-CAH enzymes throughout nature. While canonical CAHs are very well-studied, the biochemical
properties of neo-CAHs are yet to be defined. We will study the foundational biochemistry and catalytic
mechanisms of the neo-CAHs through enzymatic characterization, structural biology, and analysis of
native post-translational modifications and sub-cellular localization. This work will provide a mechanistic
understanding of neo-CAH enzyme catalysis and will yield basic insight into novel chemistry used to
produce bioactive plant molecules. Simultaneously, we will investigate the widespread occurrence of
neo-CAHs throughout nature. Each neo-CAH identified thus far has mutations in conserved active site
residues that are essential for canonical CAH function. Similar mutations are found in other
uncharacterized CAH family proteins within plants, bacteria, and animals, suggesting that CAHs have
unappreciated biosynthetic functions in multiple kingdoms of life. We will leverage these distinguishing
mutations to identify and functionally characterize other neo-CAH enzymes - including homologs from
medicinal plants, microbes, and humans - to better define the metabolic capacity of this protein family.
Through this work, we will a) provide insight on a previously unknown class of metabolic enzyme that
likely has broader biosynthetic roles in nature, and b) further determine how conserved enzymes can
gain new function to yield the striking structural and functional diversity of natural metabolites.
