Studies on ovalbumin: V. The amino acid composition and some properties of chicken, duck, and turkey ovalbumins

Abstract

The ovalbumins from chicken, duck, and turkey eggs were prepared by ammonium sulphate fractionation and purified by isoelectric focusing in a pH gradient from 3 to 6. Amino acid analyses show a closer relationship between turkey and chicken ovalbumins than between duck and chicken ovalbumins. Major differences in composition are in sulphydryl, disulphide, and methionine content (chicken 4, 1, and 15; duck 2, 1, and 23; and turkey 3, 3, and 14 groups per mole respectively). Carbohydrate is present in the three proteins in similar amounts. No N-terminal amino acid could be detected, but O-terminal proline was identified in the three proteins. Electrophoretic properties of the purified proteins were in agreement with the results of other workers on the electrophoresis of whole egg whites, and their hydrodynamic properties indicated a close similarity in size and shape. Both duck and turkey ovalbumins were converted to more heat-stable forms when exposed to pH 10 at 40°C, conditions similar to those required to convert chicken ovalbumin to S-ovalbumin. © 1970 CSIRO.