Guanosine triphosphate

Uses

Energy transfer

GTP is involved in energy transfer within the cell. For instance, a GTP molecule is generated by one of the enzymes in the citric acid cycle. This is tantamount to the generation of one molecule of ATP, since GTP is readily converted to ATP with nucleoside-diphosphate kinase (NDK).

Genetic translation

During the elongation stage of translation, GTP is used as an energy source for the binding of a new amino-bound tRNA to the A site of the ribosome. GTP is also used as an energy source for the translocation of the ribosome towards the 3' end of the mRNA.

Microtubule dynamic instability

During microtubule polymerization, each heterodimer formed by an alpha and a beta tubulin molecule carries two GTP molecules, and the GTP is hydrolyzed to GDP when the tubulin dimers are added to the plus end of the growing microtubule. Such GTP hydrolysis is not mandatory for microtubule formation, but it appears that only GDP-bound tubulin molecules are able to depolymerize. Thus, a GTP-bound tubulin serves as a cap at the tip of a microtubule to protect it from depolymerization; and, once the GTP is hydrolyzed, the microtubule begins to depolymerize and shrink rapidly.

Mitochondrial function

The translocation of proteins into the mitochondrial matrix involves the interactions of both GTP and ATP. The importing of these proteins plays an important role in several pathways regulated within mitochondria, such as converting oxaloacetate to phosphoenolpyruvate (PEP) in gluconeogenesis.

Precursor for synthesis of riboflavin

GTP, in combination with ribulose 5-phosphate, are the precursor compounds for the synthesis of riboflavin (vitamin B2).

Biosynthesis

In the cell, GTP is synthesized through many processes including:

• as a byproduct of the succinyl-CoA to succinate conversion catalysed by the succinyl-CoA synthetase enzyme as part of the citric acid cycle;
• through exchanges of phosphate groups from ATP molecules by the nucleoside-diphosphate kinase, an enzyme tasked with maintaining an equilibrium between the concentrations of different nucleoside triphosphates.

References

References

1. Berg, JM. (2002). "Biochemistry". WH Freeman and Company.
2. Solomon, EP. (2005). "Biology".
3. Gwen V. Childs. "Microtubule structure". cytochemistry.net.
4. Sepuri, Naresh Babu V.. (16 January 1998). "GTP Hydrolysis Is Essential for Protein Import into the Mitochondrial Matrix". Journal of Biological Chemistry.
5. (2020). "Present Knowledge in Nutrition, Eleventh Edition". Academic Press (Elsevier).