Creatine kinase
Creatine kinase | |||||||||
---|---|---|---|---|---|---|---|---|---|
ExPASy NiceZyme view | | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
Gene Ontology | AmiGO / QuickGO | ||||||||
|
Creatine kinase (CK), also known as creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzyme (EC 2.7.3.2) expressed by various tissues and cell types. CK catalyses the conversion of creatine and uses adenosine triphosphate (ATP) to create phosphocreatine (PCr) and adenosine diphosphate (ADP). This CK enzyme reaction is reversible and thus ATP can be generated from PCr and ADP.
In tissues and cells that consume ATP rapidly, especially
Clinically, creatine kinase is assayed in blood tests as a marker of damage of CK-rich tissue such as in myocardial infarction (heart attack), rhabdomyolysis (severe muscle breakdown), muscular dystrophy, autoimmune myositides, and acute kidney injury.[4]
Types
In the cells, the
While mitochondrial creatine kinase is directly involved in the formation of phosphocreatine from mitochondrial ATP, cytosolic CK regenerates ATP from ADP, using PCr. This happens at intracellular sites where ATP is used in the cell, with CK acting as an in situ ATP regenerator.
gene | protein |
---|---|
CKB | creatine kinase, brain, BB-CK |
CKBE | creatine kinase, ectopic expression |
CKM | creatine kinase, muscle, MM-CK |
CKMT1A, CKMT1B | creatine kinase mitochondrial 1; ubiquitous mtCK; or umtCK |
CKMT2 | creatine kinase mitochondrial 2; sarcomeric mtCK; or smtCK |
Isoenzyme patterns differ in tissues. Skeletal muscle expresses CK-MM (98%) and low levels of CK-MB (1%). The
Protein structure
The first structure of a creatine kinase solved by X-ray protein crystallography was that of the octameric, sarcomeric muscle-type mitochondrial CK (s-mtCK) in 1996.,[6] followed by the structure of ubiquitous mitochondrial CK (u-mtCK) in 2000.[7] Both mt-CK isoforms form octameric structures (built of 4 banana-like dimers) with a four-fold symmetry and a central channel.[8][9][7] The atomic structure of the banana-shaped, dimeric cytosolic brain-type BB-CK was solved in 1999 at a resolution of 1,4
Functions
Mitochondrial mtCK and cytosolic CK are connected in a so-called PCr/Cr-shuttle or circuit. PCr generated by mtCK in mitochondria is shuttled to cytosolic CK that is coupled to ATP-dependent processes, e.g. ATPases, such as acto-myosin ATPase and calcium ATPase involved in muscle contraction, and sodium/potassium ATPase involved in sodium retention in the kidney. The bound cytosolic CK accepts the PCr shuttled through the cell and uses ADP to regenerate ATP, which can then be used as an energy source by the ATPases (CK is associated intimately with the ATPases, forming a functionally coupled
Thus, CK enhances skeletal, cardiac, and smooth muscle contractility, and is involved in the generation of
Laboratory testing
Serum Creatine kinase | |
---|---|
muscle damage.[14] | |
Test of | The amount of creatine kinase in the blood.[14] |
CK is often determined routinely in a
Creatine kinase in the blood may be high in health and disease. Exercise increases the outflow of creatine kinase to the blood stream for up to a week, and this is the most common cause of high CK in blood.[17] Furthermore, high CK in the blood may be related to high intracellular CK such as in persons of African descent.[18]
Finally, high CK in the blood may be an indication of damage to CK-rich tissue, such as in
Furthermore, the isoenzyme determination has in the past been used extensively as an indication for myocardial damage in heart attacks. Troponin measurement has largely replaced this in many hospitals, although some centers still rely on CK-MB.
Nomenclature
This enzyme is often listed in medical literature under incorrect name "creatinine kinase". Creatinine is not a substrate or a product of the enzyme.[22]
See also
References
- S2CID 21911841.
- ^ PMID 1731757.
- S2CID 10404672.
- PMID 26760521.
- PMID 16236486.
- ^ Fritz-Wolf et al. 1996 http://publicationslist.org/data/theo.wallimann/ref-135/Fritz-Wolf-sMtCK%20structure.pdf
- ^ a b Eder et al. 2000 http://publicationslist.org/data/theo.wallimann/ref-101/Eder-X-ray.uMtCK.pdf
- ^ Schnyder et al. 1990 http://publicationslist.org/data/theo.wallimann/ref-184/Schnyder%201990%20Crystallization%20and%20preliminary%20X-ray%20of%20MtCk%20J%20Mol%20Biol.pdf
- ^ Schnyder et al. 1991 http://publicationslist.org/data/theo.wallimann/ref-180/SchnyderT_Gross-MtCK-crystal-EMs.pdf
- PMID 10595529.
- ^ Hornemann et al. 2000 http://publicationslist.org/data/theo.wallimann/ref-96/Hornmann-CK-dimer.pdf
- S2CID 6006006.
- PMID 32572751.
- ^ a b "Creatine Kinase (CK)". labtestsonline.org. Retrieved 2019-12-24.
- OCLC 76262148.
- OCLC 56446391.
- S2CID 7188988.
- PMID 22438879.
- S2CID 5619524.
- S2CID 5126493.
- S2CID 10818939.
- PMID 33214021.
External links
- Simply stated at mdausa.org
- Creatine+Kinase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- CPK isoenzymes test MedlinePlus Encyclopedia: 003504
- CK at Lab Tests Online