Hi there,

Difficult to say if you are not stating first what "U" stands for and what "1000" means... Usually one unit U in enzymology is one µmol/min... But obviously it is not the case here as the unit is U/mL/min.

I am still not sure about U and 1000 mean. If I can find out I will know you later. Thanks for rapid reply. Can you please suggest me something alternative?

According to me, the equation should be:

(U/ml/min)=Glucose Conc. X Dilution Factor / 1000 X Incubation time X ml of enzyme used

Because U means µmol, and you compared end product with the standard curve of glucose (which is expressed in mM). So you put value of generated glucose molecules in terms of mM in the formula. To convert the mM into µmol, you have to divide it with 1000. You know well about dilution factor and incubation time. So you can find your U/ml/min of your enzyme activity in this way.

Tehmina Saleem Khan thanks a lot for your rapid reply.

My standard curve glucose unit is mg/ml.

Suppose if I get the free glucose conc. is 0.5 mg/ml, Dilution factor 1/50, Incubation time 20 min, use 1ml of enzyme with 49 ml of water for dilution then my enzyme activity come 6.94 U/ml/min.

But according your equation I get 0.0000005 umol/min.

What should I do now?

Enzyme unit is usually defined as mikromole substrate converted or product formed per minute. Usually you then give how many units 1 mg of your enzyme corresponds to. In your case you have an enyme solution, so either you give it per ml enyme or if you know the enzme concentration you could convert it.

You have calculated correctly but U/ml/min is confusing.

It should be mikromole/ml/min, where it is mikromole glucose formed per ml enzyme solution per minute. Thus your enzyme unit corresponds to mikromole, if you really want to use enzyme unit define it as mikromole/min and then you would have 6.9 U/ml. (I would give 6.9 mikromole/ml/min.)

Remember to state the complete reaction conditions, otherwise your enzyme activity can not be compared with other determinations.

Mr. Anders O Magnusson thank you very much for your kind reply. Yes the Unit I stated is micro-mole/ml/min. I knew that U means micro-mole /ml/min. Now you assured me that my equation is correct. Thank a lot again for your kind help.

If you want to measure the cellulase activity accoding to standard curve which is made using various concentration of glucose in mg/ml, you can determine the enzyme activity as follows.

1. liberated glucose (mg/ml) during reaction can be calculated accoding to standard curve with Absobance difference betwenn before and after reaction.

2. In order to glucose amount leberated during reaction, you should multifly "1" with reaction volume, resulting the glucose amount in mg.

3. For converting mg glucose into umol glucose, please multifly "2" with 1000umol/mmol and 1mmol glucose/180 mg, resulting the glucose amount in umol

4. Since unit of cellulase activity is usually difined as the enzyme amount liberating 1 umol glucose per mim, you should devide "3" with reaction time (min). At this point, you can obtain the enzyme activity in unit (=umol glucose/min).

5. To determine the specific activity of your enzyme, you can devide "4" with purified enzyme amount in mg. Sure you can devide "4" with used enzyme volume, but the resulting activity is not specific activity.

I hope that the above content will help you.