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Nigerian Society for Experimental Biology
ISSN: 0795-8080
Vol. 17, No. 2, 2005, pp. 129-136
Bioline Code: bk05018
Full paper language: English
Document type: Research Article
Document available free of charge

Biokemistri, Vol. 17, No. 2, 2005, pp. 129-136

 en Regulatory Effect Of Divalent Cations On Rat Liver Alkaline Phosphatase Activity: How Mg2+ Activates (And Inhibits) The Hydrolysis Of P-nitrophenylphosphate
Arise, Rotimi O.; Bolaji, Femi F.; Jimoh, Olalekan A.; Adebayo, Joseph O.; Olorunniji, Femi J. & Malomo, Sylvia O.


The concentration-dependent stimulation of rat liver alkaline phosphatase (ALP) catalyzed hydrolysis of para- nitrophenylphosphate (pNPP) was studied. ALP displayed some activity even in the absence of exogenous Mg2+. Kinetic analyses show that activation by Mg2+ is exerted at the Vmax level without necessarily enhancing the affinity of the enzyme for the ion. However, the hyperbolic activation operates only within the optimal level of 0 to 5mM concentrations of the metal ion. Higher concentrations were actually inhibitory in a pure non-competitive manner. Mg2+, either as an activator (optimal concentrations) or inhibitor (supra-optimal levels) exerts its action via a Vmax effect with only negligible effect on Kmfor the substrate.

Magnesium ion, alkaline phosphatase, supra optimal regulation

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