Reverse micelles in organic solvents: a medium for the biotechnological use of extreme halophilic enzymes at low salt concentration |
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Authors: | Marhuenda-Egea Frutos C Piera-Velázquez Sonsoles Cadenas Chiquinquirá Cadenas Eduardo |
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Institution: | Facultad de Ciencias, Universidad de Alicante, 03080 Alicante, Spain. frutos@ua.es |
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Abstract: | Alkaline p-nitrophenylphosphate phosphatase (pNPPase) from the halophilic archaeobacterium Halobacterium salinarum (previously halobium) was solubilized at low salt concentration in reverse micelles of hexadecyltrimethyl-ammoniumbromide in cyclohexane with 1-butanol as co-surfactant. The enzyme maintained its catalytic properties under these conditions. The thermodynamic "solvation-stabilization hypothesis" has been used to explain the bell-shaped dependence of pNPPase activity on the water content of reverse micelles, in terms of protein-solvent interactions. According to this model, the stability of the folded protein depends on a network of hydrated ions associated with acidic residues at the protein surface. At low salt concentration and low water content (the ratio of water concentration to surfactant concentration; w0), the network of hydrated ions within the reverse micelles may involve the cationic heads of the surfactant. The bell-shaped profile of the relationship between enzyme activity and w0 varied depending on the concentrations of NaCl and Mn2+. |
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Keywords: | alkaline phosphatase archaea CTAB Halobacterium |
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