Aggregation and inhibition of rat intestinal alkaline phosphatase by high concentrations of calcium. Reversibility of the processes

Figures & data

Figure 1.  A: IAP activity before and after EGTA addition. B: IAP activity with different calcium concentrations obtained after calcium addition to IAP that was previously treated with EGTA 50 mmole/L. C: Western blot of IAP before (lane 1) and after EGTA addition (lane 2) and after 50 mmole/L calcium addition (lane 3). Data are expressed as mean ± SD (n = 4).

Table I.  Molecular mass and isoelectric point obtained by 2D-electrophoresis for the dimer and the aggregated form with and without calcium addition.

Calcium, mmole/L	Molecular form	Molecular mass, kDa	Isoelectric point
0	Dimer	162 ± 13 (n = 4)	4.35 ± 0.02
0	Aggregated form	469 ± 33 (n = 4)^*	4.35 ± 0.02
50	Dimer	168 ± 39 (n = 4)	4.85 ± 0.06^†
50	Aggregated form	441 ± 62 (n = 4)^*	4.85 ± 0.06^†

^* Represent significant differences respect to the dimer, Student's t test

^† Represent significant differences respect to the enzyme without calcium, Student's t test (p < 0.05).

Figure 2.  A: IAP activity before and after calcium addition. B: IAP activity as a function of calcium concentration. Calcium concentrations of the horizontal axis are obtained after different additions of EGTA to the solution that started with 50 mmole Ca/L. C: Western blot of IAP before (lane 1) and after Ca^{2 +} addition (lane 2) and after EGTA addition (lane 3) to obtain 0 mmole/L free calcium. Data are expressed as mean ± SD (n = 4).