Purification and Characterization of Trypsin Inhibitor from Yellowfin Tuna (Thunnus Albacores) Roe

Abstract

Trypsin inhibitor was purified to homogeneity from the roe of yellowfin tuna (Thunnus albacores) by heat treatment at 60C for 10 min, followed by column chromatographies on Sephacryl S-200, Sephadex G-50 and DEAE-cellulose. The trypsin inhibitor was purified 11.29-fold with a yield of 46.02%. Yellowfin tuna trypsin inhibitor migrated as a single band using native polyacrylamide gel electrophoresis. Purified trypsin inhibitor had an apparent molecular weight of 70 kDa when analyzed using sodium dodecyl sulfate–polyacrylamide gel electrophoresis and size exclusion chromatography. No inhibitory activity was obtained under reducing condition of β-mercaptoethanol. Maximal activity was recorded at pH 7.0 and 50C. The purified inhibitor was stable in the temperature range of 20–60C for 10 min and in the pH range of 5–8. NaCl concentration up to 3% did not significantly affect the inhibitory activity of purified trypsin inhibitor. However, the activity decreased when trypsin inhibitor was incubated with metal ions (Cu+, Na+, Mg2+ and Ca2+) at ambient temperature for 30 min. Practical Applications Trypsin inhibitor from yellowfin tuna (Thunnus albacores) roe, the by-products of tuna processing, can be purified. The yellowfin tuna trypsin inhibitor is a salt-stable peptide and could be useful for food applications, especially surimi.