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Ca 2+ –Surfactant Interactions Affect Enzyme Stability in Detergent Solutions
Author(s) -
Stoner Michael R.,
Dale Douglas A.,
Gualfetti Peter J.,
Becker Todd,
Randolph Theodore W.
Publication year - 2005
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp050149k
Subject(s) - pulmonary surfactant , micelle , chemistry , enzyme , proteases , dissociation (chemistry) , amylase , proteolysis , dissociation constant , protease , critical micelle concentration , divalent , chromatography , aqueous solution , biochemistry , organic chemistry , receptor
Abstract Detergent proteases and amylases generally bind Ca 2+ ions. These bound ions enhance enzyme stability, reducing the rates of degradative reactions such as unfolding and proteolysis. Thus, surfactant aggregates, such as micelles, affect protease and amylase stability indirectly, by competing with the enzymes for Ca 2+ ions. Dissociation constants for Ca 2+ interactions with anionic surfactant micelles are in the 10 − 3 to 10 − 2 M range. These interactions are weak relative to enzyme‐Ca 2+ interactions ( K d of order 10 − 6 M). However, surfactant is typically present at much higher concentration than enzyme, and it is the Ca 2+ –micelle equilibrium that largely determines the amount of free Ca 2+ available for binding to enzymes. The problem of surfactant‐mediated Ca 2+ removal from enzymes can be avoided by adding calcium to a detergent formulation in an amount such that the concentration of free Ca 2+ is around 10 − 5 M.