You could make use of product binding energy to drive the reaction forward while the substrate/product is bound to the enzyme. But enzymes that pull that trick are barely "enzymes" - they stay stuck to the first product they make until something else uses some energy to release it. You can't change the equilibrium constant of the overall reaction - that would violate basic thermodynamics.
This sounds a lot like a homework question I would assign my undergrads! Phoebe ---- Original message ---- >Date: Tue, 18 May 2010 09:39:49 -0600 >From: Maia Cherney <ch...@ualberta.ca> >Subject: Re: [ccp4bb] Is it possible to mutate a reversible epimerase into an inreversible one? >To: CCP4BB@JISCMAIL.AC.UK > >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: rj...@cam.ac.uk >> <mailto:rj...@cam.ac.uk> >> Cambridge CB2 0XY, U.K. www-structmed.cimr.cam.ac.uk >> Phoebe A. Rice Assoc. Prof., Dept. of Biochemistry & Molecular Biology The University of Chicago phone 773 834 1723 http://bmb.bsd.uchicago.edu/Faculty_and_Research/01_Faculty/01_Faculty_Alphabetically.php?faculty_id=123 RNA is really nifty DNA is over fifty We have put them both in one book Please do take a really good look http://www.rsc.org/shop/books/2008/9780854042722.asp
