Detection of Protease Inhibitors in the Egg Yolk of Hen and Alteration of Their Activities during Embryonic Development

Abstract

An inhibitory activity against bovine trypsin was found to exist in the egg yolk of hen. This activity increased with the progress of embryonic development. Egg yolk homogenates prepared from the eggs at 0 days and 16 days incubation were treated with acetone and then ethanol-ether (1:1). The residues were extracted with Tris-HCl buffer, pH 8.0, and fractionated with ammonium sulfate. Both of the partially purified preparations inhibited bovine chymotrypsin and bacterial alkaline protease in addition to bovine trypsin. As to the anti-tryptic activity, the inhibitor prepared from the egg yolk of 16th day of incubation was more active than the inhibitor from the yolk prior to incubation. On the other hand, the former inhibitor was more active than the latter against chymotrypsin and bacterial alkaline protease. These inhibitors were fairly stable over the pH range from 1 to 12, at 70°C, pH 7.6, and even in the presence of 8M urea at a neutral pH, while they were labile when treated with 0.1M NaOH at room temperature or heated to 90°C at pH 7.6, Both inhibitors showed no effect on the endogeneous acid protease which was found in the egg yolk.