- 期刊
Reverse micelles in organic solvents: a medium for the biotechnological use of extreme halophilic enzymes at low salt concentration
摘要
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 ＂salvation-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; w_0), 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 w_0 varied depending on the concentrations of NaCl and Mn^(2+).