Search

Amylases from the midgut gland of wild Farfantepenaeus subtilis (Perez-Farfante, 1967) and Litopenaeus schmitti (Burkenroad, 1936), and farmed Litopenaeus vannamei (Boone, 1931) were characterized through studies on the effect of inhibitor and metallic ions, optimal pH and temperature, thermal stability and zymograms. The substrate zymogram revealed nine, eight, ten and seven amylolytic bands from F. subtilis, L. schmitti, adults and juveniles L. vannamei, respectively. Total amylolytic activity in the farmed shrimp was three times as high as that of the wild specimens. Amylases from all species exhibited residual activity above 85% at alkaline pH (7.0–8.0), with optimal temperature between 40 and 50°C. None of the enzymes from the species were thermally stable at temperatures above 55°C. Alpha-amylase activity in F. subtilis and L. schmitti was totally inhibited by Type I inhibitor at 50 and 100 µg.mL-1, while enzymes from adult and juvenile L. vannamei retained 43.5 ± 1.98 and 22.5 ± 0.65% of t...

The harpacticoid copepod Tisbe biminiensis has been tested as live prey in marine crustacean and fish larviculture. The aim of the present study was to characterize the proteinases in the crude extract of T. biminiensis. Trypsin activity was assayed in the crude extract prepared by the homogenization of specimens reared under controlled laboratory conditions and fed on diatoms and commercial fish food. The physical-chemical and kinectics parameters were determined using BApNA as substrate. Optimal pH and temperature were 9.0 and 55uC, respectively. This enzyme was thermostable until 50uC. Using BApNA as substrate, the Km was 0.59 mM and the proteolytic activity was strongly inhibited by specific trypsin inhibitors. However, the presence of other proteases was observed using substrateSDS-PAGE. Eight caseinolytic bands were observed in the zymogram, four of them were not inhibited by classical mammalian trypsin inhibitors. Trypsin from T. biminiensis showed similar properties to those described for species used in commercial aquaculture. These results demonstrate that T. biminiensis may be a source of proteases, including trypsin-like enzymes.