High-affinity binding of riboflavin and FAD by immunoglobulins from normal human serum |
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Authors: | C D Watson H C Ford |
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Affiliation: | Department of Pathology, Wellington School of Medicine, Wellington Hospital, New Zealand. |
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Abstract: | The binding of [3H]FAD and [3H]riboflavin to a pooled, human plasma immunoglobulin fraction was studied. For each flavin, the data fit best a model with two binding sites of high affinity and a class of sites of lower affinity. The dissociation constants estimated for the two high affinity sites were 1.73 nM and 0.078 nM for [3H]FAD and 2.43 nM and 0.068 nM for [3H]riboflavin. The results of studies with a series of possible competitors suggested that the flavin ring system was an important determinant of the binding. Other studies showed that the binding reaction was largely enthalpy-driven. Our findings show that normal human immunoglobulins contain one or more species that bind riboflavin and FAD with very high affinity. |
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