Function
The overall effect of NDKs is to transfer a phosphate group from a nucleoside triphosphate to a nucleoside diphosphate. Starting with adenosine diphosphate GTP and ADP, the activity of NDK produces GDP and 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
Read more about this topic: Nucleoside-diphosphate Kinase
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