Reverse micelles in organic solvents: a medium for the biotechnological use of extreme halophilic enzymes at low salt concentration.
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+.
Marhuenda-Egea
Frutos C
FC
Facultad de Ciencias, Universidad de Alicante, 03080 Alicante, Spain. frutos@ua.es
Piera-Velázquez
Sonsoles
S
Cadenas
Chiquinquirá
C
Cadenas
Eduardo
E
D019843:Archaeal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D001709:Biotechnology / Q000379:methods; D004798:Enzymes / Q000302:isolation & purification / Q000378:metabolism*; D019617:Halobacterium salinarum / Q000201:enzymology; D008823:Micelles; D009930:Organic Chemicals; D009994:Osmolar Concentration; D012996:Solutions
D019843:Archaeal Proteins; D004798:Enzymes; D008823:Micelles; D009930:Organic Chemicals; D012996:Solutions