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 Ι.3 lipase and had a conserved GXSXG motif around the catalytic Ser residue. Its optimal temperature was 20-25 °C, lower than in most other subfamily Ι.3 lipases. The lipase exhibited about 30 % of maximal activity at 5 °C. The optimal pH value was 8.0. The activity was strongly inhibited by EDTA and was highly dependent on Ca(2+). 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.
[Show abstract][Hide abstract] ABSTRACT: Lipases/acyltransferases catalyse acyltransfer to various nucleophiles preferentially to hydrolysis even in aqueous media with high thermodynamic activity of water (a
w >0.9). Characterization of hydrolysis and acyltransfer activities in a large range of temperature (5 to 80 °C) of secreted recombinant homologous lipases of the Pseudozyma antarctica lipase A superfamily (CaLA) expressed in Pichia pastoris, enlighten the exceptional cold-activity of two remarkable lipases/acyltransferases: CpLIP2 from Candida parapsilosis and CtroL4 from Candida tropicalis. The activation energy of the reactions catalysed by CpLIP2 and CtroL4 was 18–23 kJ mol−1 for hydrolysis and less than 15 kJ mol−1 for transesterification between 5 and 35 °C, while it was respectively 43 and 47 kJ mol−1 with the thermostable CaLA. A remarkable consequence is the high rate of the reactions catalysed by CpLIP2 and CtroL4 at very low temperatures, with CpLIP2 displaying at 5 °C 65 % of its alcoholysis activity and 45 % of its hydrolysis activity at 30 °C. These results suggest that, within the CaLA superfamily and its homologous subgroups, common structural determinants might allow both acyltransfer and cold-active properties. Such biocatalysts are of great interest for the efficient synthesis or functionalization of temperature-sensitive lipid derivatives, or more generally to lessen the environmental impact of biocatalytic processes.
[Show abstract][Hide abstract] ABSTRACT: A novel cold-adapted lipase (designated as LipYY31) was obtained from a psychrotrophic Pseudomonas sp. YY31. The strain YY31 was gram-negative, rod shaped, motile by means of one polar flagellum, and exhibited chemotaxis toward oil droplets under a microscope. The strain displayed remarkable degradation of edible oil and fat even at 5 °C. The LipYY31 DNA fragment contains an open reading frame of 1,410 bp which encoded a protein of 470 amino acids with an estimated molecular mass of 49,584 Da. LipYY31 showed high sequence similarity to those of subfamily Ι.3 lipase and had a conserved GXSXG motif around the catalytic Ser residue. Its optimal temperature was 25-30 °C, and it retained 20-40 % of its activity at 0-5 °C. The optimal pH value was 8.0. The activity was strongly inhibited by Cd(2+), Zn(2+), EDTA and was highly dependent on Ca(2+). Tricaprin and p-nitrophenyl caprate were the most favorable substrates among the triglycerides and p-nitrophenyl esters, respectively. LipYY31 also had high activity towards natural substrates including edible vegetable oils and animal fat. Furthermore, LipYY31 was very active and stable in the presence of several detergents and organic solvents. In particular, the lipase exhibited high stability against organic solvents such as methanol, ethanol, and isopropanol.
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