Abstract
Peptides were separated from αs1-casein digested with pepsin, trypsin and/or chymotrypsin by ultrafiltration with a Diaflo membrane YM 5 (cut off: Mw. 5, 000). Molecular weights of most peptides in the trypsin or chymotrypsin digest ranged from 3, 460 to 245, while those of most peptides in the pepsin digest ranged from 1, 400 to 181 and those in the digest with the combination of the 3 proteases were smaller than 1, 400. The binding between intact αs1-casein and its IgG antibody was little inhibited by the 3 protease digest, and inhibited slightly by the pepsin, trypsin or chymotrypsin digest; each digest required more than 1, 000 times the concentration of intact αs1-casein to give a 25% inhibition. The IgG antibody titer in antisera obtained via the 10th injection of the pepsin, trypsin or chymotrypsin digest was only one or two orders of magnitude lower than that in antiserum obtained by the injection of intact αs1-casein, while the antibody titer induced by the 3 protease digest was four orders of magnitude lower. On the other hand, the anaphylactic sensitizing capacity of the antisera with regard to digests was more than three orders of magnitude lower than that of the antiserum with regard to intact αs1-casein.
