Why do the amino groups in EDTA deprotonate first, in contrast to amino acids? We know that in amino acids, carboxylic acid groups deprotonate first than the amine groups. For example, in alanine, $\mathrm{p}K_\mathrm{a,\ce{COOH}} = 2.34$, $\mathrm{p}K_\mathrm{a,\ce{NH3+}} = 9.69$ according to this page.

But according to the structures of EDTA as searched from Google, and from this extract from p.325 of Analytical Chemistry, 8e by Christian, et al.:


  At sufficiently low pH, the nitrogens can also be protonated and this diprotonated EDTA can be considered a hexaprotic acid. However, this occurs at a very low pH and EDTA is almost never used under such conditions.


the hydrogens of these amino groups seem to be deprotonated first before those of the four carboxylic acid groups. Why is this so?
The carboxylates deprotonate first followed by the amines.  The pKa values for the carboxylates ar 0.0, 1.5, 2.0, and 2.66.  The amines have pKa values of 6.16 and 10.24.  Ref. Harris.  Quantitative Chemical Analysis.