A psychrotrophic Pseudomonas sp. TK-3 was isolated from dirty and cool stream water in Toyama, Japan from which we cloned and characterized the bacterial lipase LipTK-3. The sequenced DNA fragment contains an open reading frame of 1,428 bp that encoded a protein of 476 amino acids with an estimated molecular mass of 50,132 Da. The lipase showed high sequence similarity to those of subfamily I (TM).3 lipase and had a conserved GXSXG motif around the catalytic Ser residue. Its optimal temperature was 20-25 A degrees C, lower than in most other subfamily I (TM).3 lipases. The lipase exhibited about 30 % of maximal activity at 5 A degrees C. The optimal pH value was 8.0. The activity was strongly inhibited by EDTA and was highly dependent on Ca2+. Tricaprylin and p-nitrophenyl caprylate were the most favorable substrates among the triglycerides and p-nitrophenyl esters, respectively. LipTK-3 also showed high activity towards natural substrates including edible vegetable oils and animal fats. Furthermore, LipTK-3 was very active and stable in the presence of several detergents, metal ions, and organic solvents. This cold-adapted lipase may prove useful for future applications.