Human intrinsic factor. Its primary structure compared to the primary structure of rat intrinsic factor.

: Human intrinsic factor was digested by trypsin and the resulting peptides purified by gelfiltration. Two peptides were sequenced to a total of 61 amino acid residues. Including the sequence for the N-terminal peptide and four cyanogen bromide peptides previously reported, we have now determined a total of 163 amino acid residues, that is a fraction of about 0.40 of the primary structure of human intrinsic factor. The 110 of the 163 residues known of human intrinsic factor are identical to the sequence of rat intrinsic factor.