Transition state analog

For other types of analogs, see Analog (disambiguation).

Transition state analogs (transition state analogues), are chemical compounds with a chemical structure that resembles the transition state of a substrate molecule in an enzyme-catalyzed chemical reaction. Enzymes interact with a substrate by means of strain or distortions, moving the substrate towards the transition state^[1] . Theory suggests that enzyme inhibitors which resembled the transition state structure would bind more tightly to the enzyme than the actual substrate^[2] . Transition state analogs can be used as inhibitors in enzyme-catalyzed reactions by blocking the active site of the enzyme. Examples of drugs that are transition state analog inhibitors include flu medications such as the neuraminidase inhibitor oseltamivir and the HIV protease inhibitors saquinavir in the treatment of AIDS.

Transition state analogue

The transition state of a structure can best be described in regards to statistical mechanics where the energies of bonds breaking and forming have an equal probability of moving from the transition state backwards to the reactants or forward to the products. In enzyme-catalyzed reactions, the overall activation energy of the reaction is lowered when an enzyme stabilizes a high energy transition state intermediate. Transition state analogs mimic this high energy intermediate but do not undergo a catalyzed chemical reaction and can therefore bind much stronger to an enzyme than simple substrate or product analogs.

Designing transition state analogue

To design a transition state analogue, the pivotal step is the determination of transition state structure of substrate on the specific enzyme of interest with experimental method, for example, kinetic isotope effect. In addition, the transition state structure can also be predicted with computational approaches as a complementary to KIE. We will explain these two methods in brief.

References

^ Silverman, Richard B. (2004). The Organic Chemistry of Drug Design and Drug Action. San Diego, CA: Elsevier Academic Press. ISBN 0-12-643732-7.
^ Copeland, R.A. (1996). "The Immunosuppressive Metabolite of Leflunomide is a Potent Inhibitor of Human Dihydroorotate Dehydrogenase". Biochemistry. 35 (4): 1270. doi:10.1021/bi952168g. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

[1] Silverman, Richard B. (2004). The Organic Chemistry of Drug Design and Drug Action. San Diego, CA: Elsevier Academic Press. ISBN 0-12-643732-7.

[2] Copeland, R.A. (1996). "The Immunosuppressive Metabolite of Leflunomide is a Potent Inhibitor of Human Dihydroorotate Dehydrogenase". Biochemistry. 35 (4): 1270. doi:10.1021/bi952168g. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

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