Enzyme activity calculation

sootyandsweep · Posted: Sun Feb 24, 2008 10:29 am Post subject: Enzyme activity calculation

Hi,
I need help calculating step 3, the moles formed per min, per ml of initial solution from the moles formed per min of the diluted solution.

Enzyme activity calculation in 4 steps

step 1 - calculating the change in conc per min from the diluted solution
A = 0.105min-1

c = A/el 0.105/6620x1 = 1.586x10-5

step 2 number of moles formed per min from the diluted solution

n=c x v diluted solution = 1ml = 0.001 litres

1.586x10-5 x 0.001 = 1.866x10-8 mol min-1

step 3- Number of moles formed per min, per ml of initial solution ?????

Initial solution is 20ul = 0.02ml

N.B. Apparently the answer is 7.93x10-7 mol ml-1 min-1- but how to get there?

Step - 4 - conversion to correct units = enzyme activity

Thanks
Question

sootyandsweep · Posted: Sun Mar 02, 2008 2:33 pm Post subject:

Anyone??

Hix3r · Regular Joined: 24 Apr 2007 Posts: 43 Location: Hungary

Okay I can't really understand this yet but here it is:

If you don't understand the process or the question, always try to get a lead from the unit. At step 1 the unit of the answer is mol/(litre*minute). It is almost what we need at step 3 only we need it like this mol/(millilitre*minute), so what do we do, we take the answer and divide it by 1000. Okay, now so we must put our thing into the first equation and then divide it by 1000.

So what changed now, that we have an initial solution and not a diluted one? Of course the volume! So the equation changes accordingly, if I deduced right:

concentration change per minute in initial solution = 0.105/(6620*0.02) = 7.93*10^-4 mol/(litre*minute)

now we divide it by 1000:

concentration (in mol/ml) change per minute in initial solution:
7.93*10^-4/1000 = 7.93-10^-7 mol/(ml*minute)

And there you have it the answer. I don't know what ther correct units are but there are two units of enzyme activity. One is katal. Which is number of mole of products per second. The other unit of enzyme activity is U and it is 1 umol product per minute. There is a diagnostically important other unit called enzyme concentration and it is U/litre. Realy the only thing now is just to divide or multiply the answer with the powers of ten, or the conversion number between minute and second (if you are really lost it's 60 seconds in a minute. - srry for that Very Happy

)

Anyway hope I helped!

sootyandsweep · Posted: Tue Mar 04, 2008 10:50 am Post subject:

Ah so simple! thanks for that. 6o seconds in a min lol Rolling Eyes