Biochemical and structural characterization of beta-carbonic anhydrase from the parasite Trichomonas vaginalis

Abstract: Trichomonas vaginalis is a unicellular parasite and responsible for one of the most common sexually transmittable infections worldwide, trichomoniasis. Carbonic anhydrases (CAs) are enzymes found in all lifeforms and are known to play a vital role in many biochemical processes in organisms including the maintenance of acid–base homeostasis. To date, eight evolutionarily divergent but functionally convergent forms of CAs (α, β, γ, δ, ζ, η, θ, and ι) have been discovered. The human genome contains only α-CAs, whereas many clinically significant pathogens express only β-CAs and/or γ-CAs. The characterization of pathogenic β- and γ-CAs provides important knowledge for targeting these biomolecules to develop novel anti-invectives against trichomoniasis. Here, we report the recombinant production and characterization of the second β-CA of T. vaginalis (TvaCA2). Light scattering analysis revealed that TvaCA2 is a dimeric protein, which was further supported with in silico modeling, suggesting similar structures between TvaCA2 and the first β-CA of T. vaginalis (TvaCA1). TvaCA2 exhibited moderate catalytic activity with the following kinetic parameters: k_cat of 3.8 × 10⁵ s⁻¹ and k_cat/K_M of 4.4 × 10⁷ M⁻¹ s⁻¹. Enzyme activity inhibition was studied with a set of clinically used sulfonamides and sulfonamide derivates. Twenty-seven out of the 39 compounds resulted in inhibition with a nanomolar range. These initial results encourage for future work entailing the design of more potent inhibitors against TvaCA2, which may provide new assets to fight trichomoniasis. Key messages: • Protozoan parasite Trichomonas vaginalis has two β-carbonic anhydrases (TvaCA1/2). • TvaCA1/TvaCA2 represents promising targets for antitrichomonal drug development. • TvaCA2 is a dimer of 20.3 kDa and possesses moderate catalytic activity. • The most efficient inhibitor was clinical drug acetazolamide with K_I of 222.9 nM. • The 39 tested sulfonamides form the basis for the design of more potent inhibitors.