[en] We examined various enzyme activity changes by intraperitoneal injection uranium and cathepsin D was purified and characterized in the carp liver. These enzyme activity changes can be used as biochemical indicator of internal exposure of uranium. The results was followings. 1) Lysosomal acid protease activities increased in the liver until sixth intraperitoneal injection of uranium, but Lysosomal acid phosphatase activities decreased in the liver until sixth injection of uranium. 2) Alkaline phosphatase activities increased in the liner until sixth injection of uranium. Malate dehydrogenase activities decreased sharply in the liver after primary injection of uranium and Any malate dehydrogenase activities was not detected after sixth injection of uranium. 3) We purified acidic proteolytic enzyme cathepsin D from liver of carp to near homogeneity. Its isolation involved acid precipitation(pH4.0), DEAE-Sepharose ion exchange, Sephadex G-100 gel permeation, Pepstatin-Sepharose inhibitor affinity chromatography. The SDS-PAGE revealed enzyme into a single polypeptide with M. W. 35,000 dalton. The pH activity curve of purified enzyme shows optimum near pH 2.6 and optimum activity was obtained at 45 deg C. Potentially these enzymes can be used as the indicator protein (biomarker) of environmental pollution. (Author)