Purification and characterization of a new inducible thermostable extracellular lipolytic enzyme from the thermoacidophilic archaeon Sulfolobus solfataricus P1

초록

A new thermostable extracellular lipolytic enzyme, induced from the thermoacidophilic archaeon Sulfolobus solfataricus P1 using corn oil as an inducer, was purified to apparent homogeneity by butanol extraction and two column chromatographies using DEAE-Sepharose followed by Butyl-Sepharose. The purified enzyme assessed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and gel filtration was approximately 45 kDa and monomeric. The maximal activity examined using p-nitrophenyl palmitate as a substrate was observed at 98 degrees C and pH 6.0. The enzyme showed remarkable thermostability: It retained 51% of its activity after 120h at 80 degrees C. In addition, the enzyme displayed extremely high stability against water-miscible alcohols, SDS, and urea, even at high concentrations. This high stability of the enzyme against protein-denaturing agents indicates a high potential in industrial applications. The enzyme has broad substrate specificity, exhibiting not only carboxylesterase activity toward short-chain acyl esters but also lipase activity toward long-chain acyl esters including triacylglycerols regardless of saturated and unsaturated fatty acids. The k(cat)/K-m ratios of the enzyme for p-nitrophenyl palmitate (C-16), the most preferable substrate among all tested, was 93.4 s(-1) mu M-1. Together, it was identified by thin-layer chromatography (TLC) that the enzyme can hydrolyze all positions of the three ester bonds in triolein. The enzyme is a serine esterase belonging to the alpha/beta hydrolase family containing a typical catalytic triad composed of serine, histidine, and aspartic acid in the active site of the enzyme. The enzyme is the first purified inducible extracellular lipolytic enzyme from archaea. (C) 2015 Elsevier B.V. All rights reserved.

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