Esterase

Summary Among the various esterases of the mouse kidney the Es-9 esterase is out-standing in that it is fully repressed in the cortical proximal tubulus in the absence of testosterone but is constitutive in the terminal parts of the proximal tubulus. Thus, this enzyme is regulated in a different way in closely neighboured sections of the tubular system. Comparing the disc electrophoretic patterns of the kidney esterases with the distribution of esterases in ultrathin sections as revealed by electron microscopy it is concluded that the Es-9 esterase is located in the mitochondria. This investigation was supported by the Deutsche Forschungsgemeinschaft.