Carboxyl-terminal proteolytic processing during biosynthesis of the lysosomal enzymes beta-glucuronidase and cathepsin D.
During pulse-chase experiments in cultured porcine kidney cells, an early 75-kilodalton (kDa) form of beta-glucuronidase is converted to a late 72-kDa form. The relative molecular weight difference between the two forms is maintained on removal of high-mannose carbohydrate with endoglycosidase H. Both forms have the same partial NH2-terminal sequence, and both migrate as single polypeptide chains following reduction, alkylation, and electrophoresis under denaturing conditions. On treatment with carboxypeptidase Y, the early form released [35S]Met faster than the late form. Thus, the late form of beta-glucuronidase is generated by COOH-terminal proteolytic processing of the early form. During similar experiments, the mass of the 30-kDa heavy chain of porcine cathepsin D decreased by about 1 kDa. The heavy chain of the two-chain enzyme is derived from the COOH terminus of a 44-kDa single-chain enzyme. On treatment with carboxypeptidase Y, the early single-chain enzyme released COOH-terminal [35S]Met and [3H]Lys faster than the later 29-kDa heavy chain. Like beta-glucuronidase, cathepsin D evidently undergoes COOH-terminal proteolytic processing during biosynthesis.
D000818:Animals; D002268:Carboxypeptidases; D002402:Cathepsin D; D002403:Cathepsins / Q000096:biosynthesis*; D002460:Cell Line; D005966:Glucuronidase / Q000096:biosynthesis*; D006868:Hydrolysis; D007668:Kidney; D008247:Lysosomes / Q000201:enzymology*; D010443:Peptide Chain Termination, Translational; D010447:Peptide Hydrolases; D013552:Swine
D005966:Glucuronidase; D002268:Carboxypeptidases; D002403:Cathepsins; D010447:Peptide Hydrolases; C022633:serine carboxypeptidase; D002402:Cathepsin D