In vitro conversion of proinsulin to insulin by cathepsin B and role of C-peptide

Summary Cathepsin B, purified from isolated islets of Langerhans, when incubated with proinsulin underin vitro conditions could convert proinsulin to insulin and C-peptide, releasing free arginine and lysine. When C-peptide, prepared from rat pancreas, was added to the incubation system consisting of proinsulin and cathepsin B, it completely inhibited the conversion of proinsulin to insulin. Communication no. 2295 from the Central Drug Research Institute, Lucknow, India.