I think you cannot. U and Katal refers to natural target substrate of the enzyme and are time and cinetics values. 

I never hear about concentration of an Enzyme, most of the time it is expresse in specifics activities for the same specific substract (and sometime it's link to protein content, but rarely a non-cinetic value)

I think you cannot. U and Katal refers to natural target substrate of the enzyme and are time and cinetics values. 

I never hear about concentration of an Enzyme, most of the time it is expresse in specifics activities for the same specific substract (and sometime it's link to protein content, but rarely a non-cinetic value)

The conversion factor (units / mg) is called "specific activity".  It's unique for each enzyme.  To answer this question, you need to know which enzyme you're referring to, and find its unit definition and specific activity.  

the easiest way is, determine the protein concentration. if the enzyme is pure, you can estimate its theoretical MW (from the sequence) and check for its absorbance at 280 nm, or you can do Bradford/Lowry (use internal standard with micro-assay if the concentration is small).

If your protein is not pure, you can check on an SDS PAGE (use silver stain if you are not sure about small contaminants) and estimate your enzyme fraction quantitatively (75%, 80%, 90%, whatever). Use this information to account for your "real" enzyme amount in your enzyme preparation.

You can make the conversión if : i) your enzyme is pure; ii) it is fully active; iii) you know the molecular weight of the enzyme; and iv) you know the turnover number of your enzyme. Provided you know them you must divide your enzyme concentration (in  IU mL-1) by kcat (in s-1) and multiply by 60 (seconds to minutes) and by the Molecular weight of the enzyme. This calculus will yield the concentration of the enzyme in micrograms per mL.

What for do you need to make this conversion? This conversion is possible even if the molecular weight is unknown. You need to know the units of U and under what conditions the activity has been calculated. But this depends on so you need the data.

To convert units to weight /volume, you have to know which enzyme is involved and how its activity is expressed. Do-it is katal (M.s-1) or I.U. (μM.min-1) or another unit?

You can convert the activity in mol. / time unit into concentration (g., mg or µg) / time unit, provided that the enzyme MW is known.

I have to correct a little of my last sentence. It’s the MW of the substrate (or the product) assayed after the enzymatic reaction. As stated in the previous answers, you cannot talk about the concentration of the enzyme, but on its specific activity (U/mg of proteins) that is also related to the purification degree of the enzyme

The only way to relate these two variables is to know the definition of unit for each enzyme. For example for heparin, a unit which is  the quantity of heparin required to keep 1 mL of cat's blood fluid for 24 hours at 0°C; is equivalent approximately to 0.002 mg of pure heparin. So a 50000 U/mL heparin would equate to 100 mg/ml.

Dear Kumar,

You may follow this online tool to calculate enzyme units in to mg or mL ok

http://www.physiologyweb.com/calculators/units_per_volume_solution_concentration_calculator.html

Here is my answer:

You can find the %protein and unit/mg protein in your distributor's products.

For example:

Elastase E7885 1MG (%protein = 68 % ; Units/mg protein = 8)

Total Elastase (protein) in E7885: 1 mg x 0.68 = 0.68 mg;

Total activity in E7885: 0.68 mg x 8 U/mg = 5.44 U;

For a solution of 1 U/mL ==>dissolve 5.44 U (or 1 mg) Elastase in 5.44 mL PBS.

hello, how could i get the amount of immobilized enzyme to be used in an enzyme assay after knowing the conc of protein bound on the support. From what I know , the activity of the immobilized enzyme could be divided with the conc of protein to get specific activity (Unit/mg protein). However how do I know the amount of immobilized enzyme that is equivalent the same amount of free enzyme that i am using.

Let say, I am going to use 0.2 mL of free enzyme.What are the amount of immobilized enzyme that is equivalent to volume of free enzyme based on the enzyme activity that I have.

Can any one tell me how to convert mg/ml to mM for proteinase-K solution ? Gaurav Kumar Vu Huy Azam Samadi Wangsa Tirta Ismaya Adrien Servent

1(mM)= 10-3 (mol/lit) = 10-6(mol/ml)

1 (mg/ml) = 103 (mM)

1 Unit of enzyme = 1 μmol (consumed substrate or production) /(time)

1 Units/mL = 1 μmol (consumed substrate or production)/(time × volume of reaction)

1 Units/mL = 10-6 mol (consumed substrate or production) × Molecular weight (g/mol) (of consumed substrate or production)/(time × volume of reaction) = 10-6 × Molecular weight (g/mol)/ (time × volume of reaction)

Nazmul Islam You need to know the molecular weight of the Enzyme as determined by Electrophoresis (as specified by the manufacturer) and also the specific activity (U/mg) which gives an idea of the concentration of protein in mg. Thereafter, divide the mass concentration by the molecular weight.

For example, if the Molecular weight of proteinase-K is 28.9 KDa

and assuming a concentration of 1 mg/ml

then, Molar concentration = 1/289000

=34.6 μM

which is the same as 0.0346 mM

For every substance to which this unit is assigned, you may be convert it into mass units, if you know how many microgram is equivalent to 1IU, For example, 1IU is equivalent to 34.7 microgram (0.0347 milligram) of insulin. You may be find the conversion factor of IU to mg on https://www.who.int/bloodproducts/catalogue/en/

Also

https://dietarysupplementdatabase.usda.nih.gov/Conversions.php