Effect of Deamination on Antigenic Properties of Casein

Abstract

Chemical alteration of the protein molecule may lead to profound changes in its antigenic properties, a fact which has been taken advantage of in the study of fundamental laws of immunology and as a method of investigation into the chemistry of proteins. The highly significant work of Landsteiner, particularly, has made use of artificial alterations of proteins to show the relation of chemical constitution to antigenic specificity. Nonantigenic substances of known composition are combined with proteins through reactive groups to form new antigenic compounds whose specificity is determined by the added radicals. Some of the synthesized protein compounds have been made by combining substances with the free amino groups of the proteins. While the change that occurs in the antigencity of the proteins is undoubtedly due to the activity of the newly added substances, it is not known how much if any of the change is the result of the loss of the activity of the free amino groups. Since this can be easily determined by the study of the effect of deamination alone, experiments were made, using casein, to compare the antigenic properties of a protein before and after the loss of free amino groups. Dunn and Lewis 1 determined the optimum conditions under which complete deamination will occur, and the procedure used in preparing deaminized casein was taken from their article.