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Abstract:
Brush-border fractions isolated from rat-kidney cortex were treated with papain and different concentrations of nonionic, cationic and anionic detergents. In this way significant differences in the solubility of aminopeptidase and alkaline phosphatase are noted, which can be related to their diverse organisation in the brush borders.
The aminopeptidase is localised on the surface of the microvillus matrix. It is released without a concomitant solubilization of alkaline phosphatase by incubation with papain and the nonionic detergent Triton X-100. The apparent molecular weights after removal with papain, anionic and nonionic detergents are 140 000, 145 000 and 168 000, respectively.
The alkaline phosphatase is localised in the matrix of the microvilli and more strongly bound than the bulk of the protein. Its apparent molecular weights are dependent on the agents used for the disorganisation of the brush borders. After incubation with papain the lowest molecular weight is obtained.