Abstract
Maillard reaction products (MRPs) participate in reactions of carbohydrate intermediates with proteins, resulting in the formation of advanced glycation end-products (AGEs). Dietary Maillard reaction products are recognized as potential chemical modifiers of human proteins. We have investigated the reaction of isolated MRPs from an asparagine–glucose model system with hemoglobin (Hb) to elucidate the binding effect of the MRPs in hemoglobin by fluorescence spectrophotometry. The tryptophan-specific fluorescence obtained for glycated hemoglobin exhibited a Stokes effect since the wavelength of the emission peak was shifted to a higher wavelength than that of native Hb. The formation of new fluorescence emission features indicates the formation of modified hemoglobin species. Fluorescence spectroscopic studies provide evidence that the conformational changes in the β-Trp 37 moiety induce motion of the distal His 64 (E7) in the heme binding pocket. This results in the formation of inactive hemichrome forms of hemoglobin which are related to blood disorders.
Highlights
Maillard Reaction Products (MRPs) are attributes of thermally processed foods, contributing to their avor, aroma and texture.[1,2,3,4] The increased consumption of Maillard reaction products (MRPs) in recent years has pointed towards their implication in the development of processes such as diabetes and degenerative diseases
We have investigated the reaction of isolated MRPs from an asparagine–glucose model system with hemoglobin (Hb) to elucidate the binding effect of the MRPs in hemoglobin by fluorescence spectrophotometry
A major signal at Rt 1⁄4 5.7 min is present which corresponds to the excess unreacted asparagine and other smaller chromatographic peaks arising from individual MRPs
Summary
Maillard Reaction Products (MRPs) are attributes of thermally processed foods, contributing to their avor, aroma and texture.[1,2,3,4] The increased consumption of MRPs in recent years has pointed towards their implication in the development of processes such as diabetes and degenerative diseases. The reaction of the discrete MRPs originated from an asparagine–glucose model system with hemoglobin was investigated a er one day and one month incubation time by uorescence excitation/emission spectrophotometry These speci c time points were selected to demonstrate short and long-term exposure, respectively, of hemoglobin to these glycated species. The Trp-speci c uorescence obtained for the glycated-Hb complexes exhibited Stokes effect which is attributed to the formation of Hb–MRPs complexes and to structural modi cation of Hb induced by the MRPs. We propose that the MRPs interact through hydrophobic and hydrogen bonding in the moiety of b-37 Trp, and the interaction perturbs the structural and functional properties of Hb. We suggest that the conformational changes at the N1H site have a direct effect in the O2 binding site forming a hemichrome, and b-37 Trp may be useful as an intrinsic probe to study the dynamic processes involved in the formation of hemichromes which are related to blood disorders.[5,8] comparison of the uorescence data in the presence and absence of the MRPs with UV resonance Raman data indicate that the microenvironment of b37Trp which includes aTyr[140] which is located in the microenvironment of b37Trp, a43Tyr, and b145Tyr is involved in the R / T transition.[8]
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