A new dihydrofolate reductase (svDHFR) was purified from a deep-sea bacterium, Shewanella violacea strain DSS12, isolated from the Ryukyu Trench (5110 m). In contrast with E. coli DHFR, the enzyme activity of svDHFR increased with increasing hydrostatic pressure up to 100 MPa, suggesting that the enzyme kinetics and structural fluctuation of svDHFR are adapted to a high-pressure environment.