Currently, our lab is using FTC-Casein protease assay kit for the quantification of protease activity and percentage inhibition. We came across FITC-Casein assay kit, which is not only cheaper, but has more number of reactions. I would like to ask my fellow researchers, who have experience with any or preferably both the kits to give some insights.
Thanks in advance.
I'm pretty sure FTC-casein and FITC-casein are the same thing, namely casein that has been heavily labeled on lysine residues (and perhaps also the N-terminus) with fluorescein isothiocyanate.
I only used it one time. Although it is a useful way of detecting proteolytic activity for some proteases, it is not well-suited for studying the kinetics of the enzymes because it is heterogeneous. In my hands, it did not give linear reaction progress curves, so initial rates could not be measured. For that purpose, I recommend using a fluorogenic or chromogenic peptide substrate with a sequence suited to the enzyme of interest.
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