Structure and catalytic activity of a dihydrofolate reductase-like enzyme from Leptospira interrogans

A dihydrofolate reductase (DHFR)-like enzyme from Leptospira interrogans (LiDHFRL) was cloned and the recombinant protein was characterized. Sequence alignment suggested that the enzyme lacked the conserved catalytic residues found in DHFR. Indeed, LiDHFRL did not catalyze the reduction of dihydrofolate by either NADH or NADPH. X-ray crystallography revealed that LiDHFRL bound NADP(H) tightly, but its active site architecture was vastly different from that of Escherichia coli DHFR (EcDHFR) and other DHFRLs. Interestingly, vanillin could serve as a substrate for LiDHFRL, demonstrating that LiDHFRL is a functional enzyme. A putative vanillin binding mode was proposed.