Sensitive enzyme immunoassay for human aldolase B.

A highly sensitive enzyme immunoassay system for measurement of aldolase B subunit (aldolase B) was established. Antisera were raised in rabbits by injecting aldolase B4 purified from human liver, and specific antibodies to aldolase B were purified by the use of a column of aldolase B4-coupled Sepharose. The purified antibody IgG was digested with pepsin to obtain the F(ab)' fragments. The antibody F(ab)' fragments were immobilized noncovalently on polystyrene balls, and the same antibody Fab' fragments were labeled with beta-D-galactosidase from Escherichia coli. The sandwich-type assay system using these reagents was sensitive and specific to aldolase B, showing no cross-reactivity with aldolase-A or aldolase-C. The minimum detection limit of the assay was 3 pg aldolase B4/assay tube. The immunoreactive aldolase B was present at high levels in the liver and kidney, and considerably in the small intestine. It was detected in all the tissues examined. Immunohistochemically, aldolase B is localized in hepatocytes, proximal renal tubular cells and epithelial cells of small intestine. Serum levels of aldolase B in healthy subjects were ranged from 33 to 202 ng/ml.