ELECTROPHORETIC SEPARATION OF MULTIPLE FORMS OF PARTICLE ASSOCIATED ACID PHOSPHATASE

Summary The acid phosphatases of rat liver mitochondrial‐lysosomal fractions have been examined by quantitative and electrophoretic means. Disruption of mitochondrial‐lysosomal material by freeze‐thawing, sonication, or by blendor treatment released approximately 55.0 to 65.0 per cent of the total acid phosphatase activity of the fraction into the unsedimentable phase. Electrophoretic preparations of this material showed a single acid phosphatase‐active site. Treatment of mitochondrial‐lysosomal fractions with 5.0 per cent Triton X‐100 released 98.0 per cent of the total acid phosphatase activity of the fraction into the unsedimentable phase. Electrophoretic preparations of this material showed two major sites of acid phosphatase activity. One of these was identical to that resolved following physical disruption. The other site was characteristically seen only after treatment with Triton X‐100. This acid phosphatase was also released by treatment with digitonin but to a lesser extent. Quantitative and electrophoretic examination indicated that both components of acid phosphatase were concentrated in the mitochondrial‐lysosomal fraction. Physical separation of the acid phosphatase released by detergent treatment from the acid phosphatase released by physical disruption was achieved. It was concluded that two categories of acid phosphatase may reside in lysosomal particles. These phosphatases differ in the nature of their binding to lysosomal structure as well as in their electrophoretic properties.