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Assay of hemoglobin A 1c using lectin from Aleuria aurantia

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ABSTRACT

Hemoglobin A1c (HbA1c) 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 HbA1c to total Hb is an important biomarker for the diagnosis of diabetes. HbA1c-binding lectins were screened from 29 sources of lectin, and the lectin from Aleuria aurantia (AAL) was revealed to have higher affinity to HbA1c than to Hb. The concentration of HbA1c 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 HbA1c with an anti-HbA1c antibody inhibited the binding, suggesting that AAL binds to the N-terminal fructosyl valine epitope of HbA1c. Higher inhibitory effect was observed for 10 mM d-fructose than for the same concentrations of l-fucose, d-fucose, or d-glucose.

No MeSH data available.


Comparison of structural formulas of fructosyl valine and the known ligands of AAL
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Fig4: Comparison of structural formulas of fructosyl valine and the known ligands of AAL

Mentions: This report revealed that AAL binds to HbA1c, which is a glucose modified Hb. This is the first report showing interaction between HbA1c and AAL, which has been shown to interact with saccharides containing l-fucose or d-arabinose. The results of the lectin-based ELISA (Fig. 2) showed that AAL has more binding affinity with HbA1c than that with Hb. Since the modification by glucose differentiates HbA1c from Hb, AAL is suggested to bind to fructosyl valine of the β-chain of HbA1c. This hypothesis is consistent with the observed inhibitory effect of the antibody against fructosyl valine (Fig. 3). This binding is explained by the broad binding affinity of lectin. AAL also binds to d-arabinose, which lacks the C-6 methyl group of l-fucose, although the binding affinity is 30 times weaker than that to l-fucose (Fujihashi et al. 2003). Figure 4 compares the structural formulas of the hypothetical ligand d-fructosyl valine and its known ligands l-fucose and d-arabinose. Three of these pyranoses share the same configuration of all four hydroxyl groups at chiral carbons (C-1, C-2, C-3, and C-4). It is possible that AAL binds to the fructosyl valine of β-chain of HbA1c, as does l-fucose-containing saccharides. However, the binding may be partially distinct from each other, which could result in the distinct inhibition in the presence of l-fucose or l-fructose.Fig. 4


Assay of hemoglobin A 1c using lectin from Aleuria aurantia
Comparison of structural formulas of fructosyl valine and the known ligands of AAL
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120163&req=5

Fig4: Comparison of structural formulas of fructosyl valine and the known ligands of AAL
Mentions: This report revealed that AAL binds to HbA1c, which is a glucose modified Hb. This is the first report showing interaction between HbA1c and AAL, which has been shown to interact with saccharides containing l-fucose or d-arabinose. The results of the lectin-based ELISA (Fig. 2) showed that AAL has more binding affinity with HbA1c than that with Hb. Since the modification by glucose differentiates HbA1c from Hb, AAL is suggested to bind to fructosyl valine of the β-chain of HbA1c. This hypothesis is consistent with the observed inhibitory effect of the antibody against fructosyl valine (Fig. 3). This binding is explained by the broad binding affinity of lectin. AAL also binds to d-arabinose, which lacks the C-6 methyl group of l-fucose, although the binding affinity is 30 times weaker than that to l-fucose (Fujihashi et al. 2003). Figure 4 compares the structural formulas of the hypothetical ligand d-fructosyl valine and its known ligands l-fucose and d-arabinose. Three of these pyranoses share the same configuration of all four hydroxyl groups at chiral carbons (C-1, C-2, C-3, and C-4). It is possible that AAL binds to the fructosyl valine of β-chain of HbA1c, as does l-fucose-containing saccharides. However, the binding may be partially distinct from each other, which could result in the distinct inhibition in the presence of l-fucose or l-fructose.Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

Hemoglobin A1c (HbA1c) 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 HbA1c to total Hb is an important biomarker for the diagnosis of diabetes. HbA1c-binding lectins were screened from 29 sources of lectin, and the lectin from Aleuria aurantia (AAL) was revealed to have higher affinity to HbA1c than to Hb. The concentration of HbA1c 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 HbA1c with an anti-HbA1c antibody inhibited the binding, suggesting that AAL binds to the N-terminal fructosyl valine epitope of HbA1c. Higher inhibitory effect was observed for 10 mM d-fructose than for the same concentrations of l-fucose, d-fucose, or d-glucose.

No MeSH data available.