Microcalorimetric study of wheat germ agglutinin binding to N-acetylglucosamine and its oligomers

1992/12/01 by Gabrielle Bains, Reiko T. Lee, Yuan C. Lee +1 · 13 citations
Agricultural and Biological Sciences · Chemical Engineering · Chemistry · #Advertising #Altmetrics #Biochemistry #Botanical Research and Chemistry #Chemical and Physical Properties in Aqueous Solutions #Chemistry #Citation #Computer science #Icon #Information retrieval #Wheat germ agglutinin #World Wide Web #thermodynamics and calorimetric analyses

paper · doi:10.1021/bi00165a012

openalex publication_date 1992/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01

Abstract

The energetics of association of wheat germ agglutinin (WGA) with N-acetylglucosamine (GlcNAc) and its beta(1,4) oligomers have been measured using isothermal titration calorimetry. Association constants of 0.4, 5.3, 11.1, 12.3, and 19.1 mM-1 and enthalpies of binding of -6.1, -15.6, -19.4, -19.3, and -18.2 kcal mol-1 were obtained at 26 degrees C for the titration of WGA with GlcNAc, (GlcNAc)2, (GlcNAc)3, (GlcNAc)4, and (GlcNAc)5, respectively. The term T delta S was always of negative value, indicating that the binding process is enthalpically driven. Titrations of WGA performed at pH 4.5 did not differ significantly from those performed at pH 7.0, suggesting that no groups with a pKa in this range are directly involved in the binding event. Also, performing the titration in a buffer system with a higher enthalpy of protonation did not change the enthalpy of binding confirming that there is no net protonation or deprotonation when WGA binds GlcNAc residues at pH 7. A model of four independent binding sites was found to adequately describe the binding curves, except in the case of (GlcNAc)4 which exhibited positive cooperativity. The energetic values are discussed within the context of the structure of the WGA-(GlcNAc)2 complex.

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