Enzyme Kinetics Question

Dan Diaz bl275 at cleveland.Freenet.Edu
Thu Apr 14 18:27:26 EST 1994


In a previous article, wgallin at gpu.srv.ualberta.ca (Warren Gallin) says:

>In Article <9404111941.AA22231 at unixg.ubc.ca>, flo at UNIXG.UBC.CA wrote:
>>Netters,
>>
>>If an enzyme has such an incredibly low activity on a substrate that you 
>>need to use equal molar amouts of enzyme to substrate, how does this 
>>affect the kinetics ?   ie can you still use the Michealis-Menten type 
>>equations even though the enzyme concentration is no longer much smaller 
>>than the substrate concentration?????
>
>
>If you need to use an equimolar amount of enzyme to substrate, it isn't an
>enzyme, it is a reactant.  The Michaelis Menten equation will not apply
>period.  Are you sure it really is equimolar?
>Warren Gallin,
>Department of Zoology, University of Alberta
>wgallin at gpu.srv.ualberta.ca

an enzyme is always an enzyme, no matter what its ratio to substrate.  an
enzyme will still very specifically catalyze a reaction which would
otherwise occur at a relatively low rate.  it will lower the energy of
activation and accelerate the rate at which equilibrium is reached.  many
cellular enzymes exist in concentrations which exceed those of their
substrates.  they are still enzymes.  the cell established what an enzymes
is and does billions of years before michaelis, menten, lineweaver, burke,
cleland, haldane and the whole lot.  doing test tube enzymology brings me
much satisfaction, but it aint necessarily what is happening in a cell.

diz



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