In some article, the enzyme activity has shown in terms of gm wet wt but, I used to measure in terms of mg of protein. Is there any difference (technical, bio-chemical) between these?
When the activity is expressed in terms of wet weight, it usually refers to the weight of a complex sample, such as tissue or plant matter, including all the water and everything else. When the activity is expressed in terms of mg of protein, it usually refers to a more simplified sample, such as the supernatant of an extract, a partially purified protein, or a purified protein.
Generally ,U/gm wet weight enzymes activities consider when the interested enzyme is intracellular and enzyme activity considered in U/mg of protein when the enzymes is extracellular which will be present in supernatant of extract....
Dear all,
Thank you for your kind answer. If I want to express the antioxidant enzyme activity in fish liver, what should be the unit to express? I used to make 10% homogenate of liver followed by centrifugation at 12,000 rcf for 10 minutes and take the supernatant for enzyme activity assay.
In your case I would use U/gm wet weight, unless you're able to quantify your enzyme somehow after the centrifugation step. You could also determine the total supernatant protein amount and give your values in U/mg total protein. Best would be if you can quantify your enzyme and convert the values to U/mg enzyme, which is a more specific value.
Hope this helps,
Arne
I think this is a matter of opinion. My preference would be units/mg protein because the liver sample has been processed by homogenization and centrifugation, which amounts to a purification step. Some of the enzyme activity may be in the pellet, so the measurement of the supernatant's activity is not necessarily representative of the liver tissue as a whole.
Enzyme activity in U/ g wet is activity calculated directly from assay while U/ mg of protein is the the specific activity calculated as Enzyme activity U/ g wet/ protein content mg/ mL
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