title: Human alkaline phosphatases. II. Metalloenzyme properties of the enzyme from human liver.
abstract: Human liver alkaline phosphatase is a metalloenzyme requiring Zn2 and Mg2 for full activity. Zn2 cannot be replaced by manganese, cobalt or calcium, whereas Mg2 can be replaced by manganese or calcium. The binding constants of the enzyme for different divalent cations were determined by the use of complexing agents. The enzyme is inhibited by a number of reducing and complexing agents such as 2-mercaptoethanol, cyanide, nitrilotriacetic acid and EDTA. From studies using these inhibitors it is suggested that there are different mechanisms of inhibition. Reversible inhibition occurs if the free Zn2 concentration is not significantly lower than 10(-12)M. Inhibition is irreversible at lower Zn2 concentrations. Evidence is given, that the human liver alkaline phosphatase possesses different zinc binding sites, which are responsible for the catalytic function and for the integrity of the enzyme structure.
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D002118:Calcium / Q000032:analysis; D004229:Dithiothreitol / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000032:analysis / Q000494:pharmacology; D008345:Manganese / Q000032:analysis; D008667:Metalloproteins / Q000378:metabolism; D011485:Protein Binding; D015032:Zinc / Q000032:analysis / Q000494:pharmacology
chemical_list: D008667:Metalloproteins; D008345:Manganese; D000469:Alkaline Phosphatase; D008274:Magnesium; D015032:Zinc; D002118:Calcium; D004229:Dithiothreitol