Lysinoalanine as a metal chelator. An implication for toxicity.

Synthetic lysinoalanine (N epsilon-DL-(2-amino-2-carboxyethyl)-L-lysine) was found to have a strong chelating ability for metals. It became colored when mixed with Cu+2 and showed absorption characteristics typical of a complex. Lysinoalanine could inactivate metalloenzymes such as carboxypeptidases A and B and yeast alcohol dehydrogenase, by removing the zinc ion from the active site. Model building for a mononuclear complex of the metal and lysinoalanine with space-filling models was possible for the LD-isomer, N epsilon-D-(2-amino-2-carboxymethyl)-L-lysine. Etiological studies of its toxicity to humans should be made because the chelating ability of lysinoalanine is sufficiently strong to remove the metal from the enzyme active center at millimolar concentration.