Biochemical and immunochemical properties of modified human neuron-specific enolase

125I-Labeled recombinant human neuron-specific enolase (R-NSE) was inadequate for RIA as a labeled antigen. The binding activity of labeled R-NSE to the antibody was markedly decreased. To supplement this defect and facilitate purification, we constructed two R-NSE derivatives, Y-NSE (one tyrosine residue was added at the N-terminal of R-NSE) and Y-NSE.H6 (six histidine residues were further added at the C-terminal of Y-NSE). The biochemical and immunochemical characteristics of these R-NSE derivatives were essentially the same to those of R-NSE. These derivatives were useful not only as standards for enzyme immunoassay (EIA), but also as labeled antigens for RIA. These results clearly indicate that the reactivity of these modified NSEs to anti-NSE antibody is almost equivalent to that of human brain gammagamma-enolase (B-NSE), and that even if the modified NSEs are labeled, they retain their binding affinities to antibodies in contrast to R-NSE.