I think that it's possible to do a mutation that affects only one way of
the reaction. You can mutate a residue that makes contacts only with the
product of the direct way or only of the reverse way.
Maia
Randy Read wrote:
> Dear Vinson,
>
> I would agree with you on choice B. There are probably many ways to
> look at it. Here are two that come to me at the moment.
>
> 1. If the reaction is reversible, then there's no opportunity to put
> energy into the system to reduce its overall entropy. So a reversible
> epimerase would be like a Maxwell's demon, violating the second law of
> thermodynamics.
>
> 2. Reversible reactions obey the principle of microscopic
> reversibility, i.e. the reaction mechanism and the transition states
> are the same in both directions. There's no way for an enzyme to
> selectively reduce the transition state barrier going in one direction
> but not the other.
>
> Regards,
>
> Randy Read
>
> On 18 May 2010, at 08:31, Vinson LIANG wrote:
>
>> Dear all,
>>
>> Sorry for this silly biochemistory question. Thing is that I have a
>> reversible epimerase and I want to mutate it into an inreversible
>> one. However, I have been told that the ΔG of a reversible reaction
>> is zero. Which direction the reaction goes depends only on the
>> concentration of the substrate. So the conclusion is,
>>
>> A: I can mutate the epimerase into an inreversible one. But it has no
>> influence on the reaction direction, and hence it has little mean.
>>
>> B: There is no way to change a reversible epimerase into an
>> inversible one.
>>
>> Could somebody please give me some comment on the two conclution?
>>
>> Thank you all for your time.
>>
>> Best,
>>
>> Vinson
>>
>>
>>
>
> ------
> Randy J. Read
> Department of Haematology, University of Cambridge
> Cambridge Institute for Medical Research Tel: + 44 1223 336500
> Wellcome Trust/MRC Building Fax: + 44 1223 336827
> Hills Road E-mail: [log in to unmask]
> <mailto:[log in to unmask]>
> Cambridge CB2 0XY, U.K. www-structmed.cimr.cam.ac.uk
>
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