Effects of lanthanum on alkaline phosphatase

To investigate the effects of lanthanum on the activities of two kinds of alkaline phosphatase (AP)-rat liver AP and bovine intestine AP, and the preliminary mechanism involved.A traditional colorimetric method was used to measure the activity of AP. The influence of La3+ on the intrinsic fluorescence of protein was studied by the method of fluorescence titration into the AP solution by LaCl3. The quenching equation was fitted based on the fluorescence spectrum, and then the binding number and the binding constants were calculated.Lanthanum increased the activity of rat liver AP, whereas it decreased that of bovine intestine AP. It was observed that the binding of La3+ quenched the fluorescence of bovine intestine AP, which indicated that La3+ could change the conformation of AP in solution. The number of binding sites and the binding constants that were calculated based on the fitted quenching equation were 78 and 2.1 x 10(4) respectively.La3+ has different effects on the activities of rat liver AP and bovine intestine AP; the binding of La3+ can induce the changes of conformation of bovine intestine AP, and inhibit its activity.PubMed02176-93