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. "MacKay Web". Archived from the original on 2015-02-25. Retrieved 2015-01-28.
  3. "Stereoelectronic".
  4. "Chem 654: Four Specialized Adaptations In Catalytic Proteins" (PDF). University of Alaska Fairbanks. 6 October 2011. Archived from the original (PDF) on 2 February 2015. Retrieved 9 November 2022.
  5. Toney, Michael D. (November 2011). "Controlling reaction specificity in pyridoxal phosphate enzymes" (PDF). Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics. 1814 (11): 1407–1418. doi:10.1016/j.bbapap.2011.05.019. PMC 3359020. PMID 21664990. Retrieved 9 November 2022.
  6. http://faculty.washington.edu/gelb/Chp9.ppt
  7. Mohammed Shahid; et al., eds. (2011). Biomedical aspects of histamine current perspectives. Dordrecht: Springer. ISBN 9789048193493.
  8. "Archived copy" (PDF). Archived from the original (PDF) on 2015-02-02. Retrieved 2015-01-28.{{cite web}}: CS1 maint: archived copy as title (link)
  9. Eliot, Andrew C.; Kirsch, Jack F. (June 2004). "Pyridoxal Phosphate Enzymes: Mechanistic, Structural, and Evolutionary Considerations" (PDF). Annual Review of Biochemistry. 73 (1): 383–415. doi:10.1146/annurev.biochem.73.011303.074021. PMID 15189147. Retrieved 9 November 2022.


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