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Keywords:

  • cold-active esterase;
  • Psychrobacter cryohalolentis ;
  • cryopeg;
  • permafrost

Abstract

A psychrotrophic gram-negative bacterium Psychrobacter cryohalolentis K5T was previously isolated from a cryopeg within Siberian permafrost and its genome has been completely sequenced. To clone and characterize potential cold-active lipases/esterases produced by Pcryohalolentis K5T, we have identified their potential genes by alignment with amino acid sequences of lipases/esterases from related bacteria. One of the targets, EstPc, was cloned and overexpressed in Escherichia coli BL21 (DE3) cells. The recombinant protein was produced with a 6x histidine tag at its C-terminus and purified by nickel affinity chromatography. Purified recombinant protein displayed maximum esterolytic activity with p-nitrophenyl butyrate (C4) as a substrate at 35 °C and pH 8.5. Activity assay conducted at different temperatures revealed that EstPc is a cold-adapted esterase which displayed more than 90% of its maximum activity at 0–5 °C. In contrast to many known cold-active enzymes, it possesses relatively high thermostability, preserving more than 60% of activity after incubation for 1 h at 80 °C. It was activated by Ca2+, Mn2+, and EDTA whereas Zn+2, Cu+2, Co+2, Ni+2, and Mg+2 inhibited it. Various organic solvents (ethanol, methanol and others) inhibited the enzyme. Most non-ionic detergents, such as Triton X-100 and Tween 20 increased the lipase activity while SDS completely inhibited it.