A thermostable GDSL family esterase-encoding gene, EstL5, was directly obtained from the genomic DNA of Geobacillus thermodenitrificans T2. Recombinant hexahistidine-tagged EstL5 was overexpressed, purified, and its biochemical properties were partially characterized. EstL5 was observed to be active within the temperature range of 0-80 degrees C, having maximal activity at 60 degrees C. Unlike most other thermostable enzymes, EstL5 displayed 24% of its highest activity at 0 degrees C. EstL5 exhibited a high level of activity within a pH range of 6.0-11.0, showing the highest activity at pH 8.0. EstL5 also retained 100% of its activity after a 12-h incubation at 55 degrees C. Furthermore, this enzyme was observed to be strongly inhibited by 10% (w/v) SDS and 0.1 mM PMSF. (C) 2012, The Society for Biotechnology, Japan. All rights reserved.