Kinetic regulation of an alkaline p-nitrophenylphosphate phosphatase from Halobacterium salinarum in low water system by Mn2+ and monovalent cations.
Reversed micelles were used as a cytoplasmic model to study the effect of the multi-ionic equilibria on kinetics of extreme halophilic enzymes. The enzymatic system used was an alkaline p-nitrophenylphosphate phosphatase from the halophilic archaeon Halobacterium salinarum (earlier halobium). This enzyme was solubilised in reversed micelles of hexadecyltrimethylammonium bromide in cyclohexane, with 1-butanol as co-surfactant. The p-nitrophenylphosphate phosphatase is a good system to study the regulation of the enzymatic activity, because it utilises manganese, water and potassium or sodium as cofactors and reacts with p-nitrophenylphosphate. Kinetic behaviour was determined by the ratio between [Mn2+] and [Na+] or [K+]. When the [Mn2+] increased and [Na+] or [K+] decreased, the kinetics showed cooperative behaviour. Rabin's model describes the kinetic behaviour of the p-nitrophenylphosphate phosphatase in reversed micelles.
Marhuenda-Egea
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División de Bioquímica, Facultad de Ciencias, Universidad de Alicante, Spain. frutos@ua.es
Piera-Velázquez
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Cadenas
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D009597:4-Nitrophenylphosphatase / Q000302:isolation & purification / Q000378:metabolism*; D002414:Cations, Monovalent / Q000494:pharmacology; D000077286:Cetrimonium; D002593:Cetrimonium Compounds; D019617:Halobacterium salinarum / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology*; D008823:Micelles; D008956:Models, Chemical; D011188:Potassium / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology*; D013501:Surface-Active Agents
D002414:Cations, Monovalent; D002593:Cetrimonium Compounds; D008823:Micelles; D013501:Surface-Active Agents; D008345:Manganese; D012964:Sodium; D009597:4-Nitrophenylphosphatase; D011188:Potassium; D000077286:Cetrimonium