Assay of hemoglobin A(1c) using lectin from Aleuria aurantia

Hemoglobin A(1c) (HbA(1c)) has an N-terminal fructosyl valine on the β-chain, and this modification is caused by the non-enzymatic glycosylation of hemoglobin (Hb). The relative concentration ratio of HbA(1c) to total Hb is an important biomarker for the diagnosis of diabetes. HbA(1c)-binding lectins were screened from 29 sources of lectin, and the lectin from Aleuria aurantia (AAL) was revealed to have higher affinity to HbA(1c) than to Hb. The concentration of HbA(1c) was determined by lectin-based enzyme-linked immunosorbent assay (ELISA) using the AAL lectin. Higher reproducibility of the assay was observed at 4 °C than at 25 and 37 °C. This observation is consistent with the known temperature-dependent behavior of lectins. Preincubation of HbA(1c) with an anti-HbA(1c) antibody inhibited the binding, suggesting that AAL binds to the N-terminal fructosyl valine epitope of HbA(1c). Higher inhibitory effect was observed for 10 mM d-fructose than for the same concentrations of l-fucose, d-fucose, or d-glucose.