Effect of non-ionic detergents on apparent enzyme mechanism: V121A mutant of Streptomyces cholesterol oxidase endowed with enhanced sensitivity towards detergents

Yoshiaki Nishiya, Mitsuo Yamashita, Yoshikatsu Murooka, Isao Fujii, Noriaki Hirayama

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One of the mutants of Streptomyces cholesterol oxidase with the Val121Ala mutation (V121A) was kinetically analysed. Although the reaction rate-substrate concentration curve of wild type follows a simple Michaelis-Menten equation, that of V121A is sigmoidal. The cooperativity was apparent and caused by non-ionic detergents that were used as a solvent of cholesterol. The concentration dependence of V121A on detergents was more significant than that of wild type, although the reaction rates of both enzymes decrease as the concentrations of detergents increase. Further experiments suggested that less hydrophobic interactions between V121A and detergents should be responsible for the apparent cooperativity. Since Val121 is in a hydrophobic loop located near the active site, the mutational effect is structurally discussed.

Original languageEnglish
Pages (from-to)609-611
Number of pages3
JournalProtein Engineering
Issue number8
Publication statusPublished - 1998 Aug 1



  • Apparent cooperativity
  • Cholesterol oxidase
  • Mutational effect
  • Non-ionic detergent
  • Streptomyces

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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