Structure of Plasteins

Abstract

THE molecular weight of the ‘plastein' precipitated from a pepsin hydrolysate of egg albumen at pH. 4 was found to be about 300 in determinations performed cryoscopically in a phenol solution¹. Since the average molecular weight of peptides in pepsin hydrolysate is between 300 and 400 ², no lengthening of peptide chains seems to take place in the formation of plastein, still less protein synthesis, as had generally been thought. For this reason we regarded the plasteins as being constituted of mixtures of cyclic peptides which are formed under the influence of certain proteolytic enzymes from low-molecular peptides in protein hydrolysates¹. Of the earlier investigators, Folley³ alone has supported the view of the low molecular-weight structure of plasteins.