i have an invertase product in U/L. i need it in Milligram quantity. how can i compare these two products?
Hi there,
What you need is the specific activity in U/mg. If you don't have the mass concentration of your enzyme solution you have to determine it yourself using Bradford assay for instance. If your solution is pure then UV Spectrum is OK for invertase determination knowing its specific extinction coefficient and its MW.
Just a cautionary note: The specific activity of an enzyme can and often does change over time, as the protein eventually loses activity. Thus, any conversion of Units to mg using specific activity values will be valid only at the moment it was assayed. Furthermore, as stated above, the protein content of a preparation is not necessarily all due to the enzyme itself, unless the solution is 100% pure enzyme. That is why enzyme activities are almost always given in Units.
I agree with above two answers. You first need to purify the protein, only then specific activity could be calculated. However some researchers partially purify the protein like by preciptation followed by dialysis and report the activity. In my opinion that is not accurate but you may get idea after seeing the picture on SDS PAGE that how many unwanted proteins are still there except your desired protein.
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