Distribution of thiol-protein disulfide oxidoreductase, insulin-glucagon proteinase and cathepsin D in different cell types of the rat liver.
Cathepsin D (EC 3.4.23.5), the insulin and glucagon degrading proteinase (IGP, EC 3.4.22.-) and the thiol-protein disulfide oxidoreductase (TPO, EC 1.8.4.2, 5.3.4.1) participate in the intracellular protein degradation, the last one also in post-protein-synthetic processing. The distribution of these enzymes was determined in isolated liver parenchymal cells, Kupffer cells and endothelial cells by means of immunochemical methods in order to further characterize these cell types. The cathepsin D content, expressed as microgram enzyme per mg protein, is about 3 fold higher in endothelial cells and about 5 to 24 fold higher in Kupffer cells than in parenchymal cells. This result confirms an earlier report which is based on the activity determination. The TPO concentration is highest in parenchymal cells with half of that concentration in Kupffer cells and one third in endothelial cells. About 0.5% of the total liver protein is represented by this enzyme. The IGP has been found to be totally absent in non-parenchymal cells. It represents, therefore, together with the glucose-6-phosphatase a valuable marker enzyme for parenchymal cells of rat liver.
D000818:Animals; D002402:Cathepsin D / Q000378:metabolism*; D004727:Endothelium / Q000166:cytology / Q000201:enzymology; D005934:Glucagon / Q000378:metabolism; D005779:Immunodiffusion; D007328:Insulin / Q000378:metabolism; D007728:Kupffer Cells / Q000201:enzymology; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D010088:Oxidoreductases / Q000378:metabolism*; D011490:Protein Disulfide Reductase (Glutathione) / Q000378:metabolism*; D051381:Rats
D007328:Insulin; D005934:Glucagon; D010088:Oxidoreductases; D011490:Protein Disulfide Reductase (Glutathione); D002402:Cathepsin D