Kininogenase Activity in Plasma Membranes and Cell Organelles from Rabbit Kidney Cortex: Subcellular Localization of Renal Kallikrein by Free-flow Electrophoresis and Density-gradient Fractionation

Subcellular fractions were prepared from a rabbit kidney cortex homogenate by density gradient and free-flow electrophoresis techniques. After enzymatic and morphologic characterization, we determined the kininogenase activity in the different fractions. This activity was present in those plasma membranes that also contained high specific activities Na-K-ATPase and in lysosomal-like particles. No activity was found in the lumen, that is, the microvillous part of the proximal tubule cell. The kallikrein-like nature of this kininogenase activity was established by several methods.