Nucleoside-diphosphate kinase

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.^[1]

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.^[1]

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 systems

Prokaryotic NDK forms a functional homotetramer.

Eukaryotic systems

There are two isoforms of NDK in humans: NDK-A and NDK-B. Both have very similar structure, and can combine in any proportion to form functional NDK hexamers.

See also

• Nucleoside
• Nucleotide

References

1. ^ ^{a b} Berg, JM; JL Tymoczko, L Stryer (2002). Biochemistry - 5th Edition. WH Freeman and Company. p. 476. ISBN 0-7167-4684-0. 

External links

• MeSH Nucleoside-Diphosphate+Kinase
• EC 2.7.4.6

This enzyme-related article is a stub. You can help Wikipedia by expanding it.v · Categories: Enzymes Enzyme stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем написать реферат Hard to Get (song) Sembrouthes Look at other dictionaries: nucleoside diphosphate kinase — A phosphotransferase reversibly catalyzing the transfer of one phosphoryl group from ATP to a nucleoside diphosphate to yield a nucleoside triphosphate and ADP …   Medical dictionary nucleoside-diphosphate kinase — nu·cleo·side di·phos·phate ki·nase (nooґkle o sīd diґfos fāt kiґnās) [EC 2.7.4.6] 1. an enzyme of the transferase class with broad specificity that catalyzes the reversible transfer of a phosphate from ATP to a nucleoside… …   Medical dictionary Nucleoside-phosphate kinase — Identifiers EC number 2.7.4.4 CAS number 9026 50 0 …   Wikipedia nucleoside-phosphate kinase — nu·cleo·side phos·phate ki·nase (nooґkle o sīd fosґfat kiґnās) [EC 2.7.4.4] any enzyme of the transferase class that catalyzes the transfer of a phosphate from ATP to a nucleoside phosphate to form a nucleoside diphosphate. The reaction …   Medical dictionary Nucleoside diphosphate kinases — Nucléoside diphosphate kinases Les nucléoside diphosphate kinases (NDKs, aussi NDPKs) sont des enzymes qui catalysent l échange d un groupement phosphate entre différents nucléoside diphosphates. Comme le cycle de Krebs produit seulement de l ATP …   Wikipédia en Français Nucléoside diphosphate kinases — Les nucléoside diphosphate kinases (NDKs, aussi NDPKs) sont des enzymes qui catalysent l échange d un groupement phosphate entre différents nucléoside diphosphates. Comme le cycle de Krebs produit seulement de l ATP, la NDP kinase sert à… …   Wikipédia en Français (deoxy)nucleoside-phosphate kinase — In enzymology, a (deoxy)nucleoside phosphate kinase (EC number|2.7.4.13) is an enzyme that catalyzes the chemical reaction:ATP + deoxynucleoside phosphate ightleftharpoons ADP + deoxynucleoside diphosphateThus, the two substrates of this enzyme… …   Wikipedia Nucleoside phosphotransferase — Identifiers EC number 2.7.1.77 CAS number 9055 37 2 …   Wikipedia Nucleoside-triphosphate—adenylate kinase — Identifiers EC number 2.7.4.10 CAS number 9026 74 8 …   Wikipedia Nucleoside-triphosphate-adenylate kinase — In enzymology, a nucleoside triphosphate adenylate kinase (EC number|2.7.4.10) is an enzyme that catalyzes the chemical reaction:nucleoside triphosphate + AMP ightleftharpoons nucleoside diphosphate + ADPThus, the two substrates of this enzyme… …   Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”