Characterization of acid phosphatase isoenzymes in human skin fibroblasts

Four to five isoenzymes of acid phosphatase have been detected in the lysosomal fraction of cultivated human skin fibroblasts by polyacrylamide gel electrophoresis at pH 4.0, while a single anionic isoenzyme was detected in the microsomal subcellular fraction. The anionic isoenzymes were easily solubilized. An attempt was made to further clarify the biochemical basis for the observed molecular heterogeneity of acid phosphatase isoenzymes. Treatment with neuraminidase did not alter the migration of isoenzymes present prior to treatment, but additional isoenzymes were detectable after treatment. Variation of concentrations of polyacrylamide gel resulted in varying rates of migration of 3 isoenzymes, permitting prediction of net charge and molecular size differences. Isoelectric focusing between pH 5.0 and pH 8.0 demonstrated 3 isoenzymes of acid phosphatase in the total cell homogenate and in the lysosomal fraction, two of which appeared to have similar isoelectric points.