title: Digestive enzymes along digestive tract of a carnivorous fish Glyptosternum maculatum (Sisoridae, Siluriformes).
abstract: This study attempted to determine the presence, distribution and levels of digestive proteases, pepsin, amylase and lipase in the homogenates of digestive tract of a freshwater, cold-adapted, carnivorous teleost of Tibet, Glyptosternum maculatum (n= 10, mean weight: 129.6±28.9 g, mean length: 195.1±16.6 mm, approximately 6 years old), at different temperatures and pH levels. The descending order of protease activity was as follows: stomach (pepsin, 16.16±0.96 U/mg protein), anterior intestine (3.18±0.25 U/mg protein), posterior intestine (1.76±0.21 U/mg protein) and middle intestine (1.52±0.23 U/mg protein). Amylase activity levels in descending order were as follows: anterior intestine (0.0062±0.0007 U/mg protein), stomach (0.0032±0.0009 U/mg protein), middle intestine (0.0023±0.0005 U/mg protein) and posterior intestine (0.0023±0.0004 U/mg protein). The highest lipase activity was found in the anterior intestine (0.83±0.25 U/mg protein), followed by posterior intestine (0.51±0.19 U/mg protein), middle intestine (0.48±0.09 U/mg protein) and stomach (0.39±0.10 U/mg protein). The optimal temperature and pH level for protease were 50°C and 9.0-10.0, respectively, along the intestine. The pepsin optima in the stomach were 30°C and 2.0 respectively. The optimal temperature for amylase was found to be 30°C along the digestive tract and the optimal pH was 7.0 in the intestine and 6.0 in the stomach. The optimal temperature and pH levels of lipase were 30°C, pH 6.0 for the stomach and 40-50°C, pH 8.0 for the intestine, respectively. Hepato-somatic index was 1.35±0.2% and relative intestine length was 0.90±0.19. The weight ratio of the stomach and intestine to body weight was 1.63±0.43% and 1.57±0.24% respectively.
authors.affiliation: College of Fisheries, Huazhong Agricultural University, Wuhan, Hubei, China.
authors.forename: D M
authors.initials: DM
authors.lastname: Xiong
authors.forename: C X
authors.initials: CX
authors.lastname: Xie
authors.forename: H J
authors.initials: HJ
authors.lastname: Zhang
authors.forename: H P
authors.initials: HP
authors.lastname: Liu
mesh_terms: D000681:Amylases / Q000378:metabolism; D000818:Animals; D002397:Catfishes / Q000502:physiology*; D004063:Digestion / Q000502:physiology*; D041981:Gastrointestinal Tract / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008049:Lipase / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D013696:Temperature
chemical_list: D008049:Lipase; D000681:Amylases; D010447:Peptide Hydrolases