Thermophilic and halophilic β-agarase from a halophilic archaeon Halococcus sp. 197A |
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Authors: | Hiroaki Minegishi Yasuhiro Shimane Akinobu Echigo Yukari Ohta Yuji Hatada Masahiro Kamekura Tadashi Maruyama Ron Usami |
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Institution: | 1. Bio-Nano Electronics Research Center, Toyo University, 2100 Kujirai, Kawagoe, Saitama, 350-8585, Japan 2. Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15, Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan 3. Halophiles Research Institute, 677-1, Shimizu, Noda, Chiba, 278-0043, Japan
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Abstract: | An agar-degrading archaeon Halococcus sp. 197A was isolated from a solar salt sample. The agarase was purified by hydrophobic column chromatography using a column of TOYOPEARL Phenyl-650 M. The molecular mass of the purified enzyme, designated as Aga-HC, was ~55 kDa on both SDS-PAGE and gel-filtration chromatography. Aga-HC released degradation products in the order of neoagarohexose, neoagarotetraose and small quantity of neoagarobiose, indicating that Aga-HC was a β-type agarase. Aga-HC showed a salt requirement for both stability and activity, being active from 0.3 M NaCl, with maximal activity at 3.5 M NaCl. KCl supported similar activities as NaCl up to 3.5 M, and LiCl up to 2.5 M. These monovalent salts could not be substituted by 3.5 M divalent cations, CaCl2 or MgCl2. The optimal pH was 6.0. Aga-HC was thermophilic, with optimum temperature of 70 °C. Aga-HC retained approximately 90 % of the initial activity after incubation for 1 hour at 65–80 °C, and retained 50 % activity after 1 hour at 95 °C. In the presence of additional 10 mM CaCl2, approximately 17 % remaining activity was detected after 30 min at 100 °C. This is the first report on agarase purified from Archaea. |
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