N-chloroamino acids cause oxidative protein modifications in the erythrocyte membrane.

The increase in the amount of oxidatively modified proteins is a hallmark of ageing and age-related disorders. This paper is aimed at a verification of the hypothesis that N-chloroamino acids, products of reaction between hypochlorite generated in vivo under pathological conditions and free amino acids, may induce oxidative modifications of erythrocyte membrane proteins. The effects of N-chloroalanine, N-chloroaspartate, N-chloroserine, N-chlorolysine and N-chlorophenylalanine were compared with that of HOCl/OCl(-). All the chlorocompounds studied (except for AspCl) induced the loss of tryptophan and formylkynurenine formation accompanied by decrease of acetylcholinesterase activity and V(max) of the enzyme, without change of K(m). Only HOCl/OCl(-) induced dityrosine formation being also the most effective in the induction of carbonyl groups formation. Protein thiol oxidation studied was observed for all chlorocompounds studied but with different efficiency. The destruction of amine groups content was evident for AlaCl, LysCl and SerCl. The formation of protein aggregates was observed, due mainly but not exclusively to the formation of disulphide bonds.