The differential effect of magnesium deficiency on isoenzymes of alkaline phosphatase (EC 3.1.3.1) in rat tissues.

1. Alkaline phosphatase (EC 3.1.3.1) from many rat tissues was separated into two or three bands by electrophoresis on polyacrylamide gel. Ten of the bands had different electrophoretic mobilities, but some were present in more than one tissue. 2. Bands from the corresponding tissues of magnesium-deficient and control rats were qualitatively similar, but there were quantitative differences in the distribution of enzyme activity between them. 3. Mg deficiency had differential effects on the absolute activity of individual bands, but two main types of response were observed. There was an increase in the activity of the first bands from liver and kidney, the second band from femur and both bands from spleen, whereas the first band from femur, the first and second bands from intestinal mucosa and the second bands of serum, liver and kidney all decreased in activity during the deficiency. 4. The change in total alkaline phosphatase activity of a tissue during Mg deficiency depended on the ratio between the enzyme components within it.