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conversion of rate to kcat?

conversion of rate to kcat? - Protocols and Methods Forum

conversion of rate to kcat? - Post Any Protocol, Method, Technique, Procedure or Tips / Troubleshooting for any Molecular Biology Technique.


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  #1  
Old 03-15-2006, 07:12 PM
j.nilsson@ucl.ac.uk
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Default conversion of rate to kcat?



Hi!

How would I go about converting the rate of an enzyme (nmol / min) to
kcat?

(Mr of enzyme is 125000 and a 0.01 ml sample was assayed(if this info
helps..?)

Im a little new to this subject thats why im asking this question...

Thanks! / Joakim

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  #2  
Old 03-15-2006, 08:26 PM
DK
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Default conversion of rate to kcat?

In article <1142449944.067837.231460@j33g2000cwa.googlegroups .com>, [Only registered users see links. ] wrote:

Assuming that under "rate of the enzyme" you mean rate under
substrate saturation (Vmax), all you need to know is
concentration of the enzyme.

Vmax=kcat * Etotal

So, find molar concentration of you enzyme, convert
the rate to M/sec, then divide the latter by the former.

DK

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  #3  
Old 03-17-2006, 01:53 PM
celsor3@iq.usp.br
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Default urea decomposition


Hi,

Allways I prepare my urea solutions at the day of use, in protein purification
protocols.

But, I want to know many time is possible storage urea containing solutions?
What aminoacids are modified by product of urea decomposition (cyanuric
acid)?.

Thanks

Celso


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  #4  
Old 03-20-2006, 09:15 AM
Dr Engelbert Buxbaum
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Default conversion of rate to kcat?

[Only registered users see links. ] wrote:


No, the data you gave are insufficient.

kcat = Vmax / [E]

So assuming that your conversion rate is in fact Vmax and not only V at
some arbitrary [S], you need the molar concentration of the enzyme. This
you can calculate from the molecular weight if the enzyme concentration
(mg/ml or the like) is given, which you didn't supply.

Oh, and when you do the calculation don't forget to convert all values
to basic units, so you get the order of magnitude right! Most errors
occur at this point.
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  #5  
Old 03-21-2006, 11:55 AM
matsn
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Default conversion of rate to kcat?

Hi! Thanks for your answer.

However,
I want to express the enzymatic rate (or V) as kcat at different points
during a reactions.

For example: The concentration of the enzyme is 1.5mg/ml and the
activity is 72 nmol/min at 5 mintues into the reaction. Then what is
the kcat at that point of the reaction.

Is this possible? Or do i need a vmax value to work around?

/Regards, Joakim

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  #6  
Old 03-30-2006, 09:13 AM
Dr Engelbert Buxbaum
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Default conversion of rate to kcat?

matsn wrote:



No, because kcat by definition is Vmax/[E]. So your calculation would
not give you kcat.

Do you want to calculate Vmax from a single time course? In that case,
look for the Henri-equation (but note that this method is not
particularly precise).
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