GTP is used for many purposes in the cell. They include being a source of energy for translation and other cellular processes, a substrate for RNA polymerase in synthesis of RNA, and a factor bound by G-proteins in cellular signalling/control mechanisms. GTP is produced by substrate level phosphorylation in the citric acid cycle reaction catalyzed by succinyl-CoA synthetase.

See also: Substrate Level Phosphorylation, Nucleotide Salvage Synthesis, De Novo Biosynthesis of Purine Nucleotides, Nucleotides, Guanine, G Proteins and Signal Transduction