protein specificity

[stone]

can somebody explain me the differences between protein specificity and protein affinity ?

thanks

[blcr11]

I'm not sure I have the best answer or not. In my mind the two can be related. Specificity would be a discriminatory function--an enzyme can discriminate between two stereoisomers of a substrate and so is specific, preferring to use one isomer over the other. Affinity would refer to binding energy; a more favorable free energy of binding implies a greater affinity for the substrate or other protein (in the case of protein-protein interactions, for example). It may sometimes be true that higher affinity implies greater specificity, but that need not be the case--it is possible to show high selectivity without high affinity, for example.