Purification and characterization of CHpro1, a thermotolerant, alkali-stable and oxidation-resisting protease of Chumathang hotspring

Metagenomic approaches are recently used for searching novel open reading frames (ORFs) coding enzymes employed in pharmaceutical, food industries, etc. In this study, a metagenomic library was constructed from Chumathang hotspring sediment DNA. The library consisted of approximately 9,000 clones and was screened for protease activity. A clone exhibiting protease activity was identified and named CHpro1. Sequencing of CHpro1 revealed that the ORF encoded a functional protein of 363 amino acids belonging to peptidase S8-S53 superfamily. CHpro1 shared 41% sequence similarity with a reported protease (subtilase family) and 35% structural similarity with the crystal structure of Pro-Tk sps. of Thermococcus kodarkaenasis. In silico modeling the 3D structure of CHpro1 showed that it has two beta sheets, 10 alpha helices and 11 strands. Catalytic triad prediction implied CHpro1 to be a serine protease. The optimum temperature and pH of the purified protease were found to be 80 °C and 11.0, respectively. The enzyme was active at 5% concentration of hydrogen peroxide and retained 60% of activity at 10% concentration. The thermotolerant, alkalophilic and oxidant stable properties of the protease make it a potential candidate for biotechnological applications.