The computer-based analysis of the pH titration data obtained in the M-A-B [M = Cu(II)/Zn(H), A = L-glutamic acid (Glu) and B = DL-2,3-diaminopropionic acid (dapa), DL-2,4-diaminobutyric acid (daba) and DL-ornithine (Orn)] ternary complex systems showed the presence of the mixed species of stoichiometry MABH and/or MAB in addition to various binary species due to ligands A and B. The results indicate the glycine-like mode of binding of Glu (A) primary ligand in both the Cu(II) and Zn(II) mixed ligand systems. The extra proton in the MABH type of species is associated with the secondary ligand (B), possibly with the terminal amino groups. However, in the dapa secondary ligand systems, the results also indicate the possibility of the attachment of the extra proton to the α-amino group. The dapa, daba and Orn secondary ligands (B) coordinate the metal in a tridentate manner in the mixed species of stochiometry MAB.