title: Partial characterization of digestive proteases in tropical gar Atractosteus tropicus juveniles.
abstract: Tropical gar (Atractosteus tropicus) is an economically and socially important freshwater species from Southeastern Mexico, with a high aquaculture potential. With this in mind, the purpose of this study was to characterize the digestive proteases of tropical gar juveniles through biochemical and electrophoretic analyses. Twenty specimens with an average weight of 73.6 ± 12.7 g were used to obtain stomach and intestinal tissue from which multienzymatic extracts were prepared. The general activities of the acid and alkaline proteases were evaluated, as well as the specific activities of trypsin, chymotrypsin, leucine aminopeptidase and carboxypeptidase A. The effect of the pH and temperature on the proteases was also analyzed, together with the composition of the multienzymatic extracts using protease inhibitors and electrophoretic tests. Results showed that A. tropicus have a functional stomach in which protein hydrolysis starts with pepsin and which contains endo- and exopeptidases (trypsin, chymotrypsin, leucine aminopeptidase and carboxypeptidase A) and proteases that are resistant to high temperatures (45 and 55 °C for alkaline and acid proteases, respectively) and pH values. Using zymogram technique, we found two acid protease isoforms (0.35 and 0.71 rf) and five alkaline protease isoforms (83.7, 43.7, 27.5, 24.0 and 19.4 kDa), which decrease or disappear with the different inhibitors. Thus, this species is considered to be a carnivore capable of adapting to its environment by consuming different types of proteins from preys and also could adapt rapidly to consume a compound diet with different animal protein sources.
authors.affiliation: Laboratorio de Acuicultura Tropical, División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), 0.5 km Carretera Villahermosa-Cárdenas, 86000, Villahermosa, Tabasco, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Guerrero-Zárate
authors.forename: C A
authors.initials: CA
authors.lastname: Alvarez-González
authors.forename: M A
authors.initials: MA
authors.lastname: Olvera-Novoa
authors.forename: N
authors.initials: N
authors.lastname: Perales-García
authors.forename: C A
authors.initials: CA
authors.lastname: Frías-Quintana
authors.forename: R
authors.initials: R
authors.lastname: Martínez-García
authors.forename: W M
authors.initials: WM
authors.lastname: Contreras-Sánchez
mesh_terms: D000818:Animals; D017756:Aquaculture / Q000379:methods; D043422:Carboxypeptidases A / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism; D004063:Digestion / Q000502:physiology*; D004586:Electrophoresis / Q000662:veterinary; D005399:Fishes / Q000378:metabolism* / Q000502:physiology; D041981:Gastrointestinal Tract / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D008800:Mexico; D010447:Peptide Hydrolases / Q000378:metabolism*; D018709:Statistics, Nonparametric; D013696:Temperature; D014357:Trypsin / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D010447:Peptide Hydrolases; D007931:Leucyl Aminopeptidase; D043422:Carboxypeptidases A; D002918:Chymotrypsin; D014357:Trypsin