Screening of New Psychrophiles Producing Useful Enzymes

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Enzymes showing the high activities at low temperature are applicable to the additives for the detergent, food processing, enzymatic synthesis of the thermolabile materials, and so on. We tried to find these enzymes from the psychrotrophic and psychrophilic bacteria grown under the extreme conditions. Two lipase-like genes were cloned to E.coli cells from Pseudomonas sp.B11-1 and Acinetobacter sp.No.6 cells which were isolated from the cold environment. The former gene encodes the 676-aminoacid protein with the molecular weight of 72,900. This lipase contains no GxSyG motif which is considered to be common in all lipases so far studied. The gene from Acinetobacter sp.No.6 encodes the 258-amino-acid protein with the molecular weight of 28,423. The primary structure of the protein is similar to that o^f beta-ketoadipate enol lactone hydrolase of Acinetobacter calcoaceticus. The activation energies in the rho-nitrophenyl-butyl-ester hydrolysis catalyzed by both enzymes were obtained from the Arrhenius plots of the reactions. The activation energies were calculated to be 11.2 and 11.3 (Kcal/mol) with the Pseudomonas enzyme and Acinetobacter enzyme, respectively. These values are lower that that in the reaction with the lipase from the mesophile, Pseudomonas aeruginosa (25Kcal/mol).