The inhibition of highly biotinylated enzymes by avidin and streptavidin has been used in the development of homogeneous assays for biotin and other analytes. Usually, this inhibition occurs in a similar fashion for both avidin and streptavidin. Specifically, the curves that relate the inhibition of the enzymatic activity with the concentration of avidin or streptavidin have a sigmoidal shape; i.e., the inhibition of the enzymebiotin conjugates increases gradually with increasing amounts of avidin or streptavidin and arrives at a plateau at high binding protein concentrations. However, when these two biotinspecific binding proteins interact with biotinylated glucose oxidase a significant difference in their inhibitory action is observed. In particular, the inhibition curves have a sigmoidal shape for streptavidin, while those for avidin exhibit a maximum ("hook") at low avidin concentrations. This difference in the reactivity of the two proteins with biotinylated enzymes influences both the shape of the dose-response curve and the detection limits of homogeneous enzyme-linked competitive binding assays for biotin.
ASJC Scopus subject areas
- Analytical Chemistry