The phosphatases are enzymes which catalyse the transfer of the phosphate radical (PO4) between the inorganic ionic state, as in sodium phosphate, and attachment to an organic radical, as in glucose 6-phosphate. There are numerous kinds of phosphatase in the body. One of these, red-cell acid phosphatase, is present in red cells and is most active under acid conditions. It has several genetic variants, distinguished by their electric charges, and hence by their speeds of migration during electrophoresis. They also differ somewhat in the strength of their enzymic activity.
The variants Pa, Pb, and PC are present in most populations with greatly varying frequencies, while Pr is found almost solely in southern Africans, and especially in the Khoisan peoples.()