Functional changes in digestive enzymes and characterization of proteases of silver carp (♂) and bighead carp (♀) hybrid, during early ontogeny

Study of digestive enzyme and partial characterization of proteases of silver carp (♂) and bighead carp (♀) hybrid during early ontogeny was performed. Specific amylase activity was observed in 4 DAH (0.07 ± 0.01 mg maltose mg protein− 1 min− 1) carp hybrid. Specific amylase activity showed polynomial relationship with the age of fish. Total protease, trypsin and chymotrypsin activities were 14.37 ± 2.21, 11.38 ± 1.67 and 2.83 ± 0.50 mUnits mg protein− 1 min− 1 in 4 DAH fish, respectively. Total protease activity showed exponential trend, whereas trypsin and chymotrypsin activities showed polynomial relationships with the increasing age of the fish. Lipase activity was 2.33 ± 0.18 mUnits in 4 DAH carp hybrid. Lipase activity showed polynomial trend with the increasing age of fish. In inhibition study, SBTI, PMSF, TLCK and TPCK inhibited the protease activity by 83.0% to 92.0%, 71.0% to 81.0%, 45.1% to 55.5% and 35.8% to 48.2%, respectively. SDS-PAGE showed the presence of various protein bands (20.9–69.4 kDa) in carp hybrid during ontogenic development. Substrate SDS-PAGE revealed the presence of several protease activity bands (19.1–73.7 kDa) in digestive tissue extract of fish during ontogenesis. Inhibition of protease activity bands in substrate SDS-PAGE with SBTI and PMSF revealed the abundance of serine proteases and inhibition of activity bands with TLCK and TPCK evidenced the presence of more than one isoform of trypsin and chymotrypsin in the digestive tissue extract of hybrid carp.