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Why is ATP rather than GTP, CTP or TTP used as the energy currency?
Because ATP has the responsibility to do so and it may because of evolution.
you can refer mitochondria and chloroplast for details how ATP is utilized for energy production.
Cis or trans? That's what matters.
Probably the result of some feedback loop throughout evolution.
My guess is as soon as ATP was being used/produced a bit more than the others, a feedback loop set in, and it became dominant.
Obviously, all 4 are used by DNA polymerases, and GTP is used by numerous receptor proteins.
I'm not aware of much use for TTP or CTP, but GTP is prominent.
So, as JackBean said: "(hint it's not that universal as is usually presented)"
The term`Energy Currency`is not accurate one . Because certain energy reactions ATP is NOT preferred as a valid so called `currency`. Evolution preferred `other` Currency ` called GTP rather than ATP . Unfortunately the term ATP being the `Universal Energy Currency` frequently mentioned in textbooks ( misleading statement since ignores the `certain exceptions` ) . Let me explain with the `evolutionary approach` so it will be clear for everybody with no argument attached to it `logically`..Why is the ATP preferred energy currency MOST OF THE TIME , BUT “ NOT ALL OF THE TIME” :
GTP is primarily used for Protein synthesis at the ribosomes . GTP hydrolysis is SLOW .* The extra amount of time prior to GTP hydrolysis (Compared to ATP) allows `the final fidelity check` to take place.Faster the hydrolysis rate the `error ` increases dramatically and the 3 dimensional structure of the final product (protein) is useless and it means all the energy used for the synthesis is wasted ... ! So when the “accuracy and order” is primarily important – GTP is preferred for the ` selective evolutionary force` for error free protein synthesis ( almost all of them CTP-GTP-TTP and ATP have same Bond energy . All nucleoside triphosphates have ΔG°' values close to -31 kJ/mol ) thermodynamically . Slow speed and accuracy for error check is utmost important in `Structural synthesis ` of proteins .
BUT when the FASTER reaction is prime importance than the ATP is the `chemical you need` , ATP has “faster hydrolysis time” compared to others ( CTP-GTP-TTP ) - Protein covalent bond formations can proceed ` faster rate with ATP ` without any concern for error in 3 dimensional structure of the protein ..
GTP is coupled to conformational changes of translational machinery.
GTP important for making reactions ` irreversible but accurate` GTP is important for fidelity of protein synthesis (proofreading after GTP hydrolysis)
So the bottom line is – MUCH FASTER SPEED OF HYDROLYSIS is the reason ATP is chosen -evolutionary vise early on- for the most reactions - BUT when the accuracy and fidelity check and irreversability of the reactions like -amino acid to amino acid bonding -of protein synthesis involved of course the `Slow but Sure Thing` the GTP is the best . Haste makes waste is also valid for the evolution ..!
http://dwb.unl.edu/Teacher/NSF/C08/C08L ... steps.html *
http://www.jiaowu.buct.edu.cn/Coursewar ... eases2.pdf ATP Dependent Hydrolysis of proteins
The above reply is very interesting, thank you! I have wondered for a while what drives protein synthesis forward in terms of energy, and why don't ribosomes also catalyse the reverse reaction of peptide formation, now I guess it's due to the GTP hydrolysis? But I also have some questions about the above post, maybe someone can help me?
Is GTP hydrolysis inherently slower than ATP hydrolysis? Surely it would just depend on the active site of the enzyme catalysing hydrolysis, and theoretically this could be achieved with ATP too?
I can see that these nucleoside triphosphates all have similar structure, so one might expect similar thermodynamic properties, and I can see how that links to similar ΔG°' values. However, actual ΔG in the cell will depend on the ratio of tri- and di-phosphorylated forms. Surely the only reason hydrolysis of ATP releases free energy is because the reaction is far from equilibrium (otherwise no energy would be released, and there would be nothing to drive ATP hydrolysis forwards) - it is kept far from equilibrium by the continual synthesis of ATP through oxidative phosphorylation. Is the ratio of GTP:GDP and therefore the energy released through hydrolysis similar?
7 posts • Page 1 of 1
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