An Alkaline Serine-Proteinase from a Bacterium Isolated from Bat Feces: Purification and Characterization

An alkaline serine-proteinase from Bacillus sp. PN51 isolated from bat feces collected in Phang Nga, Thailand, was purified and characterized. The molecular mass was estimated to be 35.0 kDa. The N-terminal 25 amino acid sequence was about 70% identical with that of Natrialba magadii halolysin-like extracellular serine protease. The enzyme showed the highest proteinase activity at 60 °C at pH 10.0. The activity was strongly inhibited by PMSF and chymostatin. The proteinase activity was not affected by the presence of 2% urea, 2% H 2 O 2 , 12% SDS, 15% triton X-100, or 15% tween 80. The proteinase preferred Met, Leu, Phe, and Tyr residues at the P 1 position, in descending order. The k cat , K m and k cat /K m values for Z-Val-Lys-Met-MCA were 16.8±0.14 min −1 , 5.1±0.28 μM, and 3.3±0.28 μM −1 min −1 respectively. This is the first report of an alkaline serine-proteinase with extremely high stability against detergents such as SDS.