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Creatine Kinase

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Creatine kinase (CK), also known as phosphocreatine kinase or creatine phosphokinase (CPK) is an enzyme (EC 2.7.3.2) expressed by various tissue types. It catalyses the conversion of creatine to phosphocreatine, consuming adenosine triphosphate (ATP) and generating adenosine diphosphate (ADP).

In tissues that consume ATP rapidly, especially skeletal muscle, but also brain and smooth muscle, phosphocreatine serves as an energy reservoir for the rapid regeneration of ATP. Thus Creatine Kinase is an important enzyme in such tissues.

Clinically, creatine kinase is assayed in blood tests as a marker of myocardial infarction (heart attack), rhabdomyolysis (severe muscle breakdown), muscular dystrophy and in acute renal failure.

There are three different isoenzymes that come from three distinct locations in the body:

  • BB: Brain, prostate, gastrointestinal, breast, ovary, lung
  • MM: Skeletal muscle
  • MB: Heart

Types

In most of the cell, the CK enzyme consists of two subunits, which can be either B (brain type) or M (muscle type). There are, therefore, three different isoenzymes: CK-MM, CK-BB and CK-MB. The genes for these subunits are located on different chromosomes: B on 14q32 and M on 19q13. In addition to those, there are two mitochondrial creatine kinases, the ubiquitous and sarcomeric form.

creatine kinase, brain
Identifiers
Symbol CKB
Alt. Symbols CKBB, CK-1
Entrez 1152
HUGO 1991
OMIM 123280
RefSeq NM_001823
UniProt P12277
Other data
EC number 2.7.3.2
Locus Chr. 14 q32.3
File:Creatine kinase.PNG
creatine kinase, muscle
Identifiers
Symbol CKM
Alt. Symbols CKMM, CK-3
Entrez 1158
HUGO 1994
OMIM 123310
RefSeq NM_001824
UniProt P06732
Other data
EC number 2.7.3.2
Locus Chr. 19 q13.2-13.3

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Media

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Podcasts & MP3s on Creatine kinase

Videos on Creatine kinase

Evidence Based Medicine

Cochrane Collaboration on Creatine kinase

Bandolier on Creatine kinase

TRIP on Creatine kinase

Clinical Trials

Ongoing Trials on Creatine kinase at Clinical Trials.gov

Trial results on Creatine kinase

Clinical Trials on Creatine kinase at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Creatine kinase

NICE Guidance on Creatine kinase

NHS PRODIGY Guidance

FDA on Creatine kinase

CDC on Creatine kinase

Books

Books on Creatine kinase

News

Creatine kinase in the news

Be alerted to news on Creatine kinase

News trends on Creatine kinase

Commentary

Blogs on Creatine kinase

Definitions

Definitions of Creatine kinase

Patient Resources / Community

Patient resources on Creatine kinase

Discussion groups on Creatine kinase

Patient Handouts on Creatine kinase

Directions to Hospitals Treating Creatine kinase

Risk calculators and risk factors for Creatine kinase

Healthcare Provider Resources

Symptoms of Creatine kinase

Causes & Risk Factors for Creatine kinase

Diagnostic studies for Creatine kinase

Treatment of Creatine kinase

Continuing Medical Education (CME)

CME Programs on Creatine kinase

International

Creatine kinase en Espanol

Creatine kinase en Francais

Business

Creatine kinase in the Marketplace

Patents on Creatine kinase

Experimental / Informatics

List of terms related to Creatine kinase

Isoenzyme patterns differ in tissues. CK-BB occurs mainly in tissues, and its levels do rarely have any significance in bloodstream. Skeletal muscle expresses CK-MM (98%) and low levels of CK-MB (1%). The myocardium (heart muscle), in contrast, expresses CK-MM at 70% and CK-MB at 25-30%. CK-BB is expressed in all tissues at low levels and has little clinical relevance.

The mitochondrial creatine kinase (CKm), which produces ATP from ADP by converting creatine phosphate to creatine, is present between the two membranes of the mitochondrion. Apart from the mitochondrial form, there are three forms present in the cytosol—CKa (in times of acute need, produces ATP in the cytosol at the cost of creatine phosphate), CKc (maintains critical concentration of creatine and creatine phosphate in the cytosol by coupling their phosphorylation and dephosphorylation respectively with ATP and ADP) and CKg (which couples direct phosphorylation of creatine to the glycolytic pathway (see glycolysis).

Laboratory testing

CK is often determined routinely in emergency patients. In addition, it is determined specifically in patients with chest pain and acute renal failure is suspected. Normal values are usually between 25 and 200 U/L. This test is not specific for the type of CK that is elevated.

Elevation of CK is an indication of damage to muscle. It is therefore indicative of injury, rhabdomyolysis, myocardial infarction, muscular dystrophy, myositis, myocarditis, malignant hyperthermia and neuroleptic malignant syndrome. It is also seen in McLeod syndrome and hypothyroidism. The use of statin medications, which are commonly used to decrease serum cholesterol levels, may be associated with elevation of the CPK level in about 1% of the patients taking these medications, and with actual muscle damage in a much smaller proportion.

Lowered CK can be an indication of alcoholic liver disease and rheumatoid arthritis.

Isoenzyme determination has 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.

Differential Diagnosis

Differential Diagnosis of Increased Total CK

Differential Diagnosis of Increased Total CK and CK-MB Ratio

CK and CK-MB Elevation During Pregnancy

  • In contrast to troponin, the utility of CK-MB for the diagnosis of AMI in pregnancy has not been validated.[1]
  • During labor and within 30 minutes of delivery, there may be up to two-fold increase in CK and CK-MB concentrations.[2][1]
  • Concentrations increase within 30 minutes of delivery and peak at 24 hours post-delivery.[2][1]
  • It is thought that both the cells in the uterus and the placenta may leak enzymes.[2][1]
  • To view changes in troponin concentration during pregnancy, click here.

See also

References

de:Creatin-Kinase it:Creatinchinasi


  1. 1.0 1.1 1.2 1.3 Sahni G (2012). "Chest pain syndromes in pregnancy.". Cardiol Clin. 30 (3): 343–67. PMID 22813362. doi:10.1016/j.ccl.2012.04.008. 
  2. 2.0 2.1 2.2 Shivvers SA, Wians FH, Keffer JH, Ramin SM (1999). "Maternal cardiac troponin I levels during normal labor and delivery.". Am J Obstet Gynecol. 180 (1 Pt 1): 122. PMID 9914590. 

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