The Alkaline Phosphatase is purified by affinity chromatography, which results in an enzyme of high specific activity and purity. Alkaline Phosphatase is Dimeric protein having a molecular weight of 140 kDa, one Zn ion is tightly bound to each subunit, and another less tightly bound is involved in the catalytic reaction. Mg stimulates the catalysis. The binding site for Mg is different to that of Zn , but will be occupied by excess Zn followed by loss of enzyme activity. 95% pure by Gel Filtration.