Immunoassay of three enolase isozymes in human serum and in blood cells.

Sandwich enzyme immunoassay procedures for measurement of three human enolase isozymes (alpha alpha, alpha gamma and gamma gamma forms) were developed by use of purified antibodies specific to the alpha or the gamma subunit of enolase. The assay systems consisted of polystyrene balls with immobilized antibody F(ab')2 fragments and antibody Fab' fragments labeled with beta-D-galactosidase from E. coli. The measurable range was from 3 pg to 10 ng of each enolase isozyme per assay tube, and the levels of the three enolases in human sera and isolated blood cells were determined. Serum samples from healthy adults contained about 60, 8, and 2 ng/ml of alpha alpha, alpha gamma, and gamma gamma enolases, respectively. Red blood cells and platelets had about 4, 1, and 0.1 ng/10(6) cells of alpha alpha, alpha gamma, and gamma gamma enolases, respectively. Lymphocytes (mononuclear cells) contained larger amounts of all three enolases (alpha alpha, 370 ng/10(6) cells; alpha gamma, 30 ng/10(6) cells; gamma gamma, 2.7 ng/10(6) cells). The levels of three enolase isozymes in sera of patients with small-cell cancer of the lung were also determined.