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Enzymes
An international journal published by the

Nigerian Society for Experimental Biology
Printed in Nigeria

Cofactor interactions in the activation of tissue non-specific alkaline phosphatase: Synergistic effects of Zn2+ and Mg2+ ions

Femi J. OLORUNNIJI*, Adedoyin IGUNNU, Joseph O. ADEBAYO, Rotimi O. ARISE and Sylvia O. MALOMO

Department of Biochemistry, University of Ilorin, P.M.B. 1515 Ilorin, Nigeria

Received 19 March 2007

MS/No BKM/2007/028, © 2007 Nigerian Society for Experimental Biology. All rights reserved. ---------------------------------------------------------------------------------------------------------------------------------------

Abstract The interactions of Mg2+ and Zn2+ ions in the activation of non-specific tissue alkaline phosphatase were investigated using crude extracts of rat kidney. Activation of alkaline phosphatase by the metal ions was accompanied by changes in the kinetic parameters of pnitrophenylphosphate hydrolysis. The results suggest some synergistic interactions between Mg2+ and Zn2+ ions in promoting the hydrolysis of p-nitrophenylphosphate by alkaline phosphatase. The results show that assays of alkaline phosphatase activity in homogenised tissue samples will give better responses if both Mg2+ and Zn2+ ions are included in the reactions
Keywords: Alkaline phosphatase; kinetics; Enzyme-cofactor interaction; synergism
* corresponding author. Email: femijohn@gmail.com

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INTRODUCTION The roles of metal ions in metalloenzymes include direct participation in catalysis, stabilization of protein structure and regulation of enzymatic activity. Membrane alkaline phosphatase (ALP) is a metal-containing enzyme that serves as a good model for the study of metal ion interactions in enzyme catalysis. Native E. coli ALP contains three metal ion binding sites (two Zn2+ sites and one Mg2+ site), and studies on their roles and interrelationships have provided some insights into the mechanism of the enzyme1. E. coli ALP
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