Unusual salt and solvent dependence of a protease from an extreme halophile

Jungbae Kim, Jonathan S. Dordick

Research output: Contribution to journalArticlepeer-review

76 Citations (Scopus)


An extracellular protease has been purified from the extreme halophile, Halobacterium halobium. The irreversible inactivation kinetics of this halophilic protease in salt concentrations below 4 M consists of autolytic and nonautolytic (steady-state denaturation) components. Addition of organic solvents has a dramatic effect on enzyme stability in low salt media. For example, in 0.36M NaCl, the inactivation rate constant for the nonautolytic component in 20% (v/v) ethylene glycol is ca. 3 orders of magnitude lower than in 20% (v/v) tetrahydrofuran. Enzyme stability in different aqueous/organic solvent mixtures correlates strongly to the salting-out capacity of the solvent. Solvents that act to increase the apparent hydrophobicity of the enzyme's core stabilize the enzyme in much the same way as salting-out salts. This mechanism is not important for the nonhalophilic protease, subtilisin Carlsberg, and demonstrates that halophilic enzymes have evolved highly specialized reaction medium requirements. Moreover, through the use of organic solvents, it is shown that high concentrations of salts are not absolutely necessary for high enzyme stability, and this may have important process considerations.

Original languageEnglish
Pages (from-to)471-479
Number of pages9
JournalBiotechnology and Bioengineering
Issue number3
Publication statusPublished - 1997 Aug 5
Externally publishedYes


  • Halophilic protease
  • Organic cosolvents
  • Salting out
  • Stability

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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