Ca2+-surfactant interactions affect enzyme stability in detergent solutions.
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.
Stoner
Michael R
MR
Department of Chemical Engineering, University of Colorado, Boulder, 80309, USA.
Dale
Douglas A
DA
Gualfetti
Peter J
PJ
Becker
Todd
T
Randolph
Theodore W
TW
D001407:Bacillus / Q000201:enzymology; D001709:Biotechnology; D002118:Calcium; D002480:Cellulase / Q000737:chemistry; D003902:Detergents; D004795:Enzyme Stability; D066298:In Vitro Techniques; D008823:Micelles; D017510:Protein Folding; D012967:Sodium Dodecyl Sulfate; D012996:Solutions; D013381:Subtilisins / Q000737:chemistry; D013501:Surface-Active Agents; D014242:Trichoderma / Q000201:enzymology; D000516:alpha-Amylases / Q000737:chemistry
D003902:Detergents; D008823:Micelles; D012996:Solutions; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; D000516:alpha-Amylases; D002480:Cellulase; D013381:Subtilisins; D002118:Calcium