High-affinity binding of riboflavin and FAD by immunoglobulins from normal human serum.
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.
Watson
C D
CD
Department of Pathology, Wellington School of Medicine, Wellington Hospital, New Zealand.
Ford
H C
HC
D001665:Binding Sites; D001667:Binding, Competitive; D004591:Electrophoresis, Polyacrylamide Gel; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism*; D008954:Models, Biological; D011485:Protein Binding; D012256:Riboflavin / Q000378:metabolism*
D007136:Immunoglobulins; D005182:Flavin-Adenine Dinucleotide; D012256:Riboflavin