Effect of inhibitors present in protein sources on digestive proteases of juvenile sea bream (Sparus aurata)

The presence of protease inhibitors in different ingredients used in fish f eeds may negatively affect their digestive utilisation. The effect of inhib itors present in several protein sources on the activity of digestive prote ases of sea bream was assessed using 'in vitro' assays. Inhibition produced by extracts of plant proteins ranged from 25 to 50 % of total activity, wh ereas that obtained using animal protein sources ranged from 1 to 20 %. The exception was ovoalbumin, which showed the highest measured value (62 %). A plot of the inhibition values obtained by changing the relative concentra tions enzyme/inhibitor resulted in different curves for different protein s ources. The use of sodium dodecyl sulphate polyacrylamide gel electrophores is (SDS-PAGE) zymograms allowed visualisation of the aforementioned differe nces in inhibition. The importance of measuring protease inhibition in the preliminary evaluation of fish feed ingredients is discussed. (C) 1999 Ifre mer/Cnrs/Inra/Ird/Cemagref/Editions scientifiques et medicales Elsevier SAS .