Concanavalin A-bound selenoprotein in human serum analyzed by graphite furnace atomic absorption spectrometry.

We developed an assay for the direct determination of selenium in serum with a Perkin-Elmer Model 4100ZL Zeeman atomic absorption spectrometer and Ag-Cu-Mg modifier. We used this assay to analyze concanavalin A-bound selenoprotein (CABSP) in human serum after concanavalin A (ConA) affinity chromatography. The CABSP was identified as a single-chain glycoprotein of 57.3 kDa. Carbohydrate units were N- and O-linked to the protein. The selenium moiety was selenocysteine. Total selenium, glutathione peroxidase (GPX; EC 1.11.1.9), ConA-bound selenium (CABS), and alpha 1-acid glycoprotein (AAG) were determined in normal subjects and patients with various pathological conditions. CABS accounted for 44.1% +/- 6.3% of total selenium in sera from normal subjects and 46.5% +/- 3.9% to 55.1% +/- 8.1% in sera from patients with a variety of diseases. Total selenium in serum was well correlated with serum CABS (r = 0.860), but not with serum GPX activity (r = 0.117), for all patients studied. Serum CABS increased in normal subjects after selenium supplementation. Serum CABSP did not behave as an acute-phase reactant, compared with AAG.