Studies on Thermophilic α-Amylase from <i>Bacillus stearothermophilus</i>:I. Some General and Physico-chemical Properties of Thermophilic α-amylase

J-STAGE
  • OGASAHARA KYOKO
    Division of Physical Chemistry, Institute for Protein Research, Osaka University
  • IMANISHI AKIRA
    Division of Physical Chemistry, Institute for Protein Research, Osaka University
  • ISEMURA TOSHIZO
    Division of Physical Chemistry, Institute for Protein Research, Osaka University

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説明

Some physico-chemical and biochemical properties of a crystalline α-amylase [EC 3. 2. 1. 1] from B. stearothermophilus Dank, strain BS-1 (thermophilic α-amyiase) were investigated. Thermophilic α-amylase was more resistant to higher temperature than B. subtilis α-amylase. Optimum temperature range for the activity of thermophilic α-amylase was found to be from 65 to 73°C within 10min incubation and it was almost 17°C higher than that of B. subtilis α-amylase. Molecular weight and intrinsic viscosity of thermophilic α-amylase were 48, 000 and 0.032 (dl/g), respectively. Thermophilic α-amylase showed a negative Cotton effect at 233mμ in the optical rotatory dispersion and two negative troughs at 210 and 225mμ. in the circular dichroism spectrum suggesting that the molecule contained a right-handed α-helical structure. The apparent content of α-helix in thermophilic α-amylase was estimated to be about 20 per cent. Molecular weight, intrinsic viscosity and content of α-helix of thermophilic α-amylase were different from those of α-amylase obtained by Campbell et al. but very close to those of B. subtilis α-amylase. It may be concluded that thermophilic α-amylase has such a globular structure as those of many other α-amylase except α-amylase obtained by Campbell et al. The difference of thermophilic α-amylase from B. subtilis α-amylase was found in the circular dichroism spectra in the 250-320mμ region and in the amino acid composition.

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