structural analyses , including digestion with trypsin and carboxypeptidases a and b , have shown that one is unmodified hb a and the other is gly-nh2 ( 142 alpha ) hb in which gly-nh2 is bound to the cooh-terminal residue of the alpha subunit ( arg 141 alpha ) via peptide bond .
C0019016
hb a
C0019046
hb