Abstract
The five cystine peptides of chymotrypsinogen B have been isolated as pairs of cysteic acid peptides by the diagonal electrophoretic technique of Brown & Hartley (1963, 1966). The sequences of these peptides have been shown to be very similar to those of chymotrypsinogen A, and indicate that both zymogens have the same pattern of disulphide bridges. The determination of the sequence of residues 14-21 in chymotrypsinogen B has shown that residue 18 differs in the chymotrypsinogens from the corresponding residue in trypsinogen. Eight differences between chymotrypsinogens A and B are found in sequences accounting for 72 of the 245 residues.