Inverse has an article on The science behind catnip’s potent powers:
Catnip’s pungent odor comes from a chemical called nepetalactone. It helps the plant repel insects.
But this research takes us further into the evolution of nepetalactone using genetic analysis. According to study co-author Benjamin Lichman, a plant biologist at the University of York, his team discovered “a suite of unusual enzymes” were responsible for nepetalactone’s kitty arousing properties.
“These enzymes are not found in any related plant species and have evolved uniquely in catmint,” Lichman says.
Nepetalactone uses a double-whammy — literally — to stupefy cats. Lichman and his colleagues discovered that while other types of mint form chemicals using only one enzyme, nepetalactone instead activates one enzyme, which sets off a chain reaction to activate a second enzyme.