Dunathan stereoelectronic hypothesis

Dunathan stereoelectronic hypothesis is a concept in chemistry to explain the stereospecefic cleavage of bonds using pyridoxal phosphate. This occurs because stereoelectronic effects controls the actions of the enzyme.[1]

History

Before the correlation between fold type and reaction correlation of proteins were understood, Harmon C. Dunathan, a chemist at Haverford College[2] proposed that the bond that is cleaved using pyridoxal is perpendicular to the system.[3] Though an important concept in bioorganic chemistry, it is now known that enzyme conformations play a critical role in the final chemical reaction.

Mode of action

The transition state is stabilized by the extended pi bond network (formation of anion).[4] Furthermore hyperconjugation caused by the extended network draws electrons from the bond to be cleaved, thus weakening the chemical bond and making it labile[5] The sigma bond that is parallel to the pi bond network will break.[6] The bond that has the highest chance of being cleaved is one with the largest HOMO-LUMO overlap.[7] This effect might be effected by electrostatic effects within the enzyme.[8]

Applications

This was seen in transferase and future interests lie in decarboxylation in various catalytic cycles.[9]

References

  1. ↑ Silverman, Richard B. (2002). The organic chemistry of enzyme-catalyzed reactions (Rev. ed.). San Diego, Calif. [u.a.]: Acad. Press. ISBN 9780126437317.
  2. ↑ http://www.haverford.edu/chem/mackay/ColinWeb/MacKay_Web.html
  3. ↑ http://chemgroups.ucdavis.edu/~toney/Stereoelectronic.html
  4. ↑ http://chem.uaf.edu/keller/Courses/654Fa11/PDF/654-10-6-11.pdf
  5. ↑ http://chemgroups.ucdavis.edu/~toney/Publications/BBA%20-%20Proteins%20and%20Proteomics%202011%20Toney.pdf
  6. ↑ http://faculty.washington.edu/gelb/Chp9.ppt
  7. ↑ editors, Mohammed Shahid ... [et al.], (2011). Biomedical aspects of histamine current perspectives. Dordrecht: Springer. ISBN 9789048193493.
  8. ↑ http://www.chem.wisc.edu/areas/organic/studsemin/steinkruger/steinkruger-sem.pdf
  9. ↑ http://www.life.illinois.edu/biochem/455/Lab%20exercises/5GOT/PLP%20enzyme%20review.pdf


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