Adenylate kinase
| Adenylate kinase | |||||||||
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3D ribbon/surface model of adenylate kinase in complex with bis(adenosine)tetraphosphate (ADP-ADP)
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| Identifiers | |||||||||
| Symbol | ADK | ||||||||
| Pfam | PF00406 | ||||||||
| InterPro | IPR000850 | ||||||||
| PROSITE | PDOC00104 | ||||||||
| SCOP | 1ake | ||||||||
| SUPERFAMILY | 1ake | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
| ADK_lid | |||||||||
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Bacillus stearothermophilus adenylate kinase
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| Identifiers | |||||||||
| Symbol | ADK_lid | ||||||||
| Pfam | PF05191 | ||||||||
| InterPro | IPR007862 | ||||||||
| PROSITE | PDOC00104 | ||||||||
| SCOP | 1ake | ||||||||
| SUPERFAMILY | 1ake | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
| Adenylate kinase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC number | 2.7.4.3 | ||||||||
| CAS number | 2598011 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
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| Search | |
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| PMC | articles |
| PubMed | articles |
| NCBI | proteins |
Adenylate kinase (EC 2.7.4.3) (also known as ADK or myokinase) is a phosphotransferase enzyme that catalyzes the interconversion of adenine nucleotides (ATP, ADP, and AMP). By constantly monitoring phosphate nucleotide levels inside the cell, ADK plays an important role in cellular energy homeostasis.
The reaction catalyzed is:
The equilibrium constant varies with condition, but it is close to 1. Thus, ΔGo for this reaction is close to zero. In muscle from a variety of species of vertebrates and invertebrates, the concentration of ATP is typically 7-10 times that of ADP, and usually greater than 100 times that of AMP. The rate of oxidative phosphorylation is controlled by the availability of ADP. Thus, the mitochondrion attempts to keep ATP levels high due to the combined action of adenylate kinase and the controls on oxidative phosphorylation.
To date there have been nine human ADK protein isoforms identified. While some of these are ubiquitous throughout the body, some are localized into specific tissues. For example, ADK7 and ADK8 are both only found in the cytosol of cells; and ADK7 is found in skeletal muscle whereas ADK8 is not. Not only do the locations of the various isoforms within the cell vary, but the binding of substrate to the enzyme and kinetics of the phosphoryl transfer are different as well. ADK1, the most abundant cytosolic ADK isozyme, has a Km about a thousand times higher than the Km of ADK7 and 8, indicating a much weaker binding of ADK1 to AMP. Sub-cellular localization of the ADK enzymes is done by including a targeting sequence in the protein. Each isoform also has different preference for NTP's. Some will only use ATP, whereas others will accept GTP, UTP, and CTP as the phosphoryl carrier.
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Wikipedia