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Abstract:
The drastic growth of the population on our
planet requires the efficient and sustainable use of our natural resources. Enzymes are indispensable tools for
a wide range of industries producing food, pharmaceuticals,
pesticides, or biofuels. Because insects constitute
one of the most species-rich classes of organisms colonizing
almost every ecological niche on earth, they have
developed extraordinary metabolic abilities to survive in
various and sometimes extreme habitats. Despite this metabolic
diversity, insect enzymes have only recently generated
interest in industrial applications because only a few
metabolic pathways have been sufficiently characterized.
Here, we address the biosynthetic route to iridoids (cyclic
monoterpenes), a group of secondary metabolites used by
some members of the leaf beetle subtribe Chrysomelina
as defensive compounds against their enemies. The ability
to produce iridoids de novo has also convergently evolved
in plants. From plant sources, numerous pharmacologically
relevant structures have already been described. In
addition, in plants, iridoids serve as building blocks for
monoterpenoid indole alkaloids with broad therapeutic
applications. As the commercial synthesis of iridoidbased
drugs often relies on a semisynthetic approach
involving biocatalysts, the discovery of enzymes from the
insect iridoid route can account for a valuable resource
and economic alternative to the previously used enzymes
from the metabolism of plants. Hence, this review illustrates
the recent discoveries made on the steps of the iridoid
pathway in Chrysomelina leaf beetles. The findings
are also placed in the context of the studied counterparts
in plants and are further discussed regarding their use in technological approaches.
