Transition State of a Creatine Molecule during Dehydration Computation Chemistry Seminar 2000 Ravi Agarwal John O’Dowd

Purpose  The purpose of our project was to determine the transition state of the dehydration of creatine into creatinine. This reaction was chosen because of our interest in creatine as a body supplement in the body.

Background Information  Creatine is an amino acid (a protein) that is produced in tiny doses by the liver, kidneys and pancreas and stored in the muscles. In food, it is found in meat and fish.  Creatine is the guanidine- derived, phosphorylated compound which maintains cellular ATP homeostasis in the higher animals.  Creatine is also a body supplement used to increase anaerobic performance.

Background Information  Creatine helps the body replenish energy through the reaction of creatine monohydrate to creatine phosphate.  Energy in the muscles comes from the reaction of adenosine triphosphate to adenosine diphosphate (ATP ADP). Creatine helps replenish energy by donating its phosphate back to ADP so the process can repeat.

Background Information  Creatinine is the dehydrated form of creatine. Its significance bio-chemically is that creatine cannot be excreted from the body. So the body dehydrates it and then excretes creatinine.

Dehydration of Creatine + H 2 0 O OH CH 2 CH 3 C NH NH 2 NH C N CH 3 CH 2 NH C--O N C

Computation Approach  The experiment began with the use of MacSpartan on a Power Macintosh. We completed our project using MacSpartan Pro.  The transition state was determined using the Semi- Empirical method of AM-1.  Due to the complexity of our molecule, the ab initio method (321G*) was impractical. We used the Semi Empirical method (AM-1) for all of calculations.

Computation Approach  First we built the creatine molecule in MacSpartan Pro. Then we ran a geometry optimization using the AM-1 basis set. Using our predictions, we used the transition search by editing the bonds so that the creatinine is formed.

The –OH group bonded to the carbon will attack the hydrogen bonded to the NH 2 The nitrogen bonds to the carbonyl. Transition Search Approach

Computational Approach  Then we ran a transition search for our prediction.  In order to determine if the molecule was a true transition state it must have one unique imaginary frequency.  After the frequency scan, our transition search was determined to be a true transition state for the dehydration of creatine.  This molecule is the transition state.

Transition State Moving hydrogen Nitrogen bonded to carbonyl.

Transition State  Has one imaginary frequency.  Follows our prediction: Nitrogen bonded to carbonyl Hydrogen on the amine moves from to the hydroxyl to form water. Calculated single point energies to determine activation energy using AM-1 basis set.

Optimized Transition State  Transition State was optimized using AM-1 basis set.

Single Point Energies kcal/mol kcal/mol kcal/mol Activation Energy: kcal/mol Creatine Transition Creatinine

Conclusion  Found transition state for dehydration of creatine based on one imaginary frequency when we scanned the transition structure.  Calculated Single Point Energies to determine activation energy. Activation energy is large so an enzyme most likely catalyzes the reaction.