Amyloid β2-microglobulin is modified with N(ε)-(carboxymethyl)lysine in dialysis-related amyloidosis

Abstract

Recent work from this laboratory revealed that advanced glycation end product was localized to amyloid deposits in patients with dialysis-related amyloidosis by immunohistochemistry using a monoclonal antibody to advanced glycation end product. To elucidate the epitope of the antibody, N(α)-p-tosyl-L-lysine-methyl ester was incubated with glucose in vitro, and then a compound reactive to the antibody was purified from the incubate by buthanol extraction, XAD-2 column chromatography, and high-performance liquid chromatography while the reactivity wits examined by enzyme linked immunosorbent assay. The purified compound was identified as N(ε)-(carboxymethyl)-N(α)-p-tosyl-L-lysine-methyl ester by using secondary ion mass spectrometry, and 1H- and 13C-nuclear magnetic resonance spectroscopy. The apitope of the antibody was identified as -CH2-NH-CH2-COOH by enzyme-linked immunosorbent assay of compounds with structures similar to N(ε)-(carboxymethyl)lysine. Immunochemical study using the antibody demonstrated the presence of N(ε)-(carboxymethyl)lysine in the β2-microglobulin dimer (molecular weight 23929) isolated from the synovium amyloid of a hemodialysis patient with dialysis-related amyloidosis. In conclusion, amyloid β2-microglobulin is modified with N(ε)-(carboxymethyl)lysine in dialysis-related amyloidosis.