Figure 1.
Negative-ion ESI mass spectra of (A) fish pepsinogen A1 and (B) activated fish pepsin A1. The measured molecular weights were 38,845 Da for the pepsinogen form (theoretical mass: 38,850.6 Da) and 34,250 Da for the activated form (theoretical mass: 34,241.2 Da). The conversion of pepsinogen to pepsin leads to a mass shift of ~ 4600 Da due to the removal of the N-terminal residues 1–38. (C) Negative-ion ESI mass spectra of pig pepsin A from Sigma, as a control (theoretical mass: 34,583.8 Da; measured mass: 34,584 Da). (D). Commassie-stained SDS-PAGE gel of fish pepsin A1 before (lane 1) and after (lane 2) activation.