Thermostable esterases screened on hyperthermophilic archaeal andbacterial strains isolated from deep-sea hydrothermal vents:Characterization of esterase activity of a hyperthermophilic archaeum,Pyrococcus abyssi

摘要

One hundred sixty thermophilic or hyperthermophilic anaerobic archaea and bacteria isolated from deep-sea hydrothermal vents were screened for esterase activity; 47 were found to be esterase positive, showing three different electrophoretic profiles of proteins following esterase staining. Characterization of the crude esterase activity of Pyrococcus abyssi was performed. P. abyssi is an anaerobic hyperthermophilic archaeum, which produces two intracellular esterases. Esterase activities up to 3.5 units/liter culture were produced by Pyrococcus abyssi in flasks. The pH and temperature optima for esterase activity were 5.8-7.8 and >70 degrees C, respectively. This crude esterase activity exhibited a half-life of 22 h at 99 degrees C and of 13 min at 120 degrees C, and retained its entire initial activity after incubation at 90 degrees C for 8.5 h without any substrate and/or cofactor. The archaeal esterase activity showed a broad range of substrate spectra, being capable of hydrolyzing triacylglycerols and aliphatic and aromatic esters, but seemed to be restricted to short-chain fatty acid esters (C-2 to C-8). Phenylmethanesulphonyl fluoride (PMSF) strongly inhibited the esterase activity. According to the substrate specificity and the inhibition pattern, the esterase activity of P. abyssi was found to be of the serine type (or B-carboxylesterases, EC 3.1.1.1).