|PDB structures||RCSB PDB PDBe PDBsum|
Nucleoside-diphosphate kinases (NDKs, also NDP Kinase, (poly)nucleotide kinases and nucleoside diphosphokinases) are enzymes that catalyze the exchange of phosphate groups between different nucleoside diphosphates. NDK activities maintain an equilibrium between the concentrations of different nucleoside triphosphates such as, for example, when GTP produced in the citric acid (Krebs) cycle is converted to ATP.
- GTP + ADP → GDP + ATP
Behind this apparently simple reaction is a multistep mechanism. The key steps are
- NDK binds a nucleoside triphosphate (NTP)
- NDK transfers a phosphate to itself, leaving a bound nucleoside diphosphate (NDP)
- NDK releases the bound nucloside diphosphate
- NDK binds another nucleoside diphosphate
- NDK transfers the phosphate to the diphosphate, creating a bound nucleoside triphosphate
- NDK releases the new nucleoside triphosphate
Each step is part of a reversible process, such that the multistep equilibrium is of the following form.
- NDK + NTP ↔ NDK~NTP ↔ NDK-P~NDP ↔ NDK-P + NDP
For the transfer of a phosphate from ATP to GDP, the reaction would proceed as
- NDK + ATP → NDK~ATP → NDK-P~ADP → NDK-P + ADP →
- NDK-P + GDP → NDK-P~GDP → NDK~GTP → NDK + GTP
Prokaryotic NDK forms a functional homotetramer.
- Berg, JM; JL Tymoczko, L Stryer (2002). Biochemistry - 5th Edition. WH Freeman and Company. p. 476. ISBN 0-7167-4684-0.
- Nucleoside-Diphosphate Kinase at the US National Library of Medicine Medical Subject Headings (MeSH)
- EC 184.108.40.206
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