Enzyme Identified Species Optimum pH Reference
Pepsin Smooth hound 2.0 Bougatef et al. [50]
Pepsin I Arctic capelin 3.7 Gildberg and Raa [48]
Pepsin II Arctic capelin 2.5 Gildberg and Raa [48]
Pepsin I European eel 3.5 Wu et al. [52]
Pepsin II European eel 2.5 Wu et al. [52]
Pepsin III European eel 2.5 Wu et al. [52]
Pepsin Greenland cod 3.5 Squires et al. [61]
Pepsin Atlantic cod 3.5 Haard [62]
Pepsin Arctic cod 3.0 Haardet al. [72]
Pepsin I Atlantic cod 3.5 Gildberg [58]
Pepsin II Atlantic cod 3.0 Gildberg [58]
Pepsin palometa 3.0–3.5 Pavliskoet al. [73]
Pepsin I Sea bream 3.0 Zhou et al. [51]
Pepsin II Sea bream 3.5 Zhou et al. [51]
Pepsin III Sea bream 3.5 Zhou et al. [51]
Pepsin IV Sea bream 3.5 Zhou et al. [51]
Pepsin Albacore tuna 2.0 Nalinanon et al. [65]
Pepsin I Mandarin fish 3.5 Zhou et al. [60]
Pepsin II Mandarin fish 3.5 Zhou et al. [60]
Pepsin III Mandarin fish 3.5 Zhou et al. [60]
Pepsin IV Mandarin fish 3.5 Zhou et al. [60]
Pepsin I African coelacanth 2.0 Tanji et al. [49]
Pepsin II African coelacanth 2.0 Tanji et al. [49]
Pepsin III African coelacanth 2.5 Tanji et al. [49]
Table 1: The optimum pH of pepsin from different fishes.