Characterization and Inhibition of a Novel Diterpene Virulence Factor from Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) remains a widespread and devastating human pathogen whose ability to infiltrate the human immune system is an active area of investigation. We have recently reported the discovery of a novel diterpene from Mtb, edaxadiene, which has the ability to arrest phagosome maturation at an early stage, presumably contributing to the early survival of Mtb in the immune system. Importantly, Mtb knockout in the committed step of edaxadiene synthesis are impaired in their ability to survive in the phagosome. In addition, the closely related but less infectious Mycobacterium bovis has a frameshift mutation in this enzyme, resulting in an inactive enzyme in vitro, further indicating involvement of edaxadiene in early infection. Together, these results indicate that this enzyme is a suitable target for drug design. In an attempt to evaluate this enzyme as a drug target, we have kinetically characterized the committed enzyme in edaxadiene synthesis and evaluated it with two sub‐nM inhibitors, which are not suitable for clinical applications, but offer a platform for further pharmacological design. Further, our kinetic characterization has indicated a mechanism for tight regulation of this pathway via divalent cation starvation during phagosomal engulfment, allowing timely and potent regulation of edaxadiene synthesis during infection.