Subcellular localization of human placental acid phosphatases

An electron microscopic study of acid p-nitrophenyl phosphatase activity in placental tissue has revealed two distinct localizations for this enzyme in the syncytiotrophoblast: within lysosome-like bodies and on the microvillous surface. The surface enzyme is distributed in an apparently random patchwork pattern over the chorionic villi. Evidence is presented which suggests that this nonlysosomal form may be phosphatase III, an enzyme which has previously been partially purified and characterized in vitro. Acid phosphatase activity was not observed in the cytotrophoblastic cells of Langhans' layer, and it was not present on microvilli of epithelial cells from uterine glands. These studies were carried out with a modified Gomori-type incubation medium containing a substantially reduced lead ion concentration together with p-nitrophenyl phosphate.