The crystal structure of Leishmania major N⁵,N¹⁰-methylenetetrahydrofolate dehydrogenase/cyclohydrolase and assessment of a potential drug target

Three enzyme activities in the protozoan Leishmania major, namely N⁵,N¹⁰-methylenetetrahydrofolate dehydrogenase/N⁵,N¹⁰-methenyltetrahydrofolate cyclohydrolase (DHCH) and N¹⁰-formyltetrahydrofolate ligase (FTL) produce the essential intermediate N¹⁰-formyltetrahydrofolate. Although trypanosomatids possess at least one functional DHCH, the same is not true for FTL, which is absent in Trypanosoma brucei. Here, we present the 2.7 Å resolution crystal structure of the bifunctional apo-DHCH from L. major, which is a potential drug target. Sequence alignments show that the cytosolic enzymes found in trypanosomatids share a high level of identity of approximately 60%. Additionally, residues that interact and participate in catalysis in the human homologue are conserved amongst trypanosomatid sequences and this may complicate attempts to derive potent, parasite specific DHCH inhibitors.