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KMID : 0545120070170040624
Journal of Microbiology and Biotechnology
2007 Volume.17 No. 4 p.624 ~ p.631
Purification and Characterization of Two Thermostable Proteases from the Thermophilic Fungus Chaetomium thermophilum
Li An-Na

Ding Ai-Yun
Chen Jing
Liu Shou-An
Zhang Ming
Li Duo-Chuan
Abstract
A ¥â-glucosidase from the algal lytic bacterium Sinorhizobium kostiense AFK-13, grown in complex media containing cellobiose, was purified to homogeneity by successive ammonium sulfate precipitation, and anion-exchange and gelfiltration chromatographies. The enzyme was shown to be a monomeric protein with an apparent molecular mass of 52 kDa and isoelectric point of approximately 5.4. It was optimally active at pH 6.0 and 40oC and possessed a specific activity of 260.4 U/mg of protein against 4-nitrophenyl-¥â-Dglucopyranoside (pNPG). A temperature-stability analysis demonstrated that the enzyme was unstable at 50oC and above. The enzyme did not require divalent cations for activity, and its activity was significantly suppressed by Hg+2 and Ag+, whereas sodium dodecyl sulfate (SDS) and Triton X-100 moderately inhibited the enzyme to under 70% of its initial activity. In an algal lytic activity analysis, the growth of cyanobacteria, such as Anabaena flos-aquae, A. cylindrica, A. macrospora, Oscillatoria sancta, and Microcystis aeruginosa, was strongly inhibited by a treatment of 20 ppm/disc or 30 ppm/disc concentration of the enzyme.
KEYWORD
Thermophile Chaetomium thermophilum, characterization, purification, thermostable protease
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