Several plasmids have been constructed which direct the synthesis of rat pepsinogen or prepepsinogen in Escherichia coli. When plasmids with the E. coli lac promoter was introduced into E. coli, a protein identified as pepsinogen or prepepsinogen by immunoreactivity and SDS-PAGE was synthesized in the form of fused protein with β-galactosidase. They constituted up to 2.5% of the total cellular protein and formed insoluble aggregate in E. coli. They were solublized by urea extraction, but no pepsin activity was detected in these proteins. In these proteins, both intra and intermolecular activation from pepsinogen to pepsin was impaired. This impairment of the activation step was probably due to the structural change of the N-terminal regions of these proteins rather than the degeneration by urea extraction.
