Proteolysis of lipotropin C-fragment takes place extracellularly to form gamma-endorphin and [methionine]enkephalin [proceedings].

The octapeptide 61-68 and the heptapeptide 61-67 do not possess the protected conformation of C-fragment. In contrast with the protracted exposure to membrane enzymes required to form [methioninelenkephalin from C-fragment, the short peptides rapidly undergo this conversion. The corresponding tripeptide Thr-Ser-Glu and dipeptide Thr-Ser were isolated. The results suggest that C-fragment is degraded in a stepwise manner, accounting for the spectrum of named peptides that have been isolated from brain.