The creatine kinase (CK), creatine kinase, creatine kinase, creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzymatic protein found in various tissues of the human body. Organs with high energy demand are present, such as striated muscle, as well as heart muscle and brain. The enzyme's function is to transfer a phosphate radical -phosphorylation- of creatine to form ATP.
CK is a high molecular weight compound - around 80 KiloDaltons - found within muscle and nerve cells. Inside the cell it is present both in the cytoplasm and in the mitochondria. It is also known as creatine phospho-kinase, or CPK.
The CK-MM, CK-MB and CK-BB fractions correspond to isoenzymes present in striated muscle tissue, cardiac and nervous system, respectively..
Although creatine kinase is intracellular, it is found circulating in the blood, available to supply the requirements in the tissues. An increase in CK values in the blood means that it has been released as a result of tissue damage.
Lesions of the skeletal and visceral muscles, or of the brain will cause elevation of the enzyme in the blood. The consequences derived from this are those derived from the disease that produces it.
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Creatine kinase favors the process of obtaining rapid energy in the tissues where it is found. The enzyme fulfills its metabolic function at the level of mitochondria and cytoplasm, in the process of muscle or brain ATP replacement. Creatine is the substrate involved in the CK-mediated reaction.
Creatine - discovered in 1832 - is an organic acid that contains nitrogen. The creatine molecule associates with the phosphate radical to form phosphocreatine - a phosphagen - an energy reserve form. CK takes phosphocreatine phosphate to produce ATP, necessary for muscle and nerve tissue activity.
In tissues that require a high energy intake, CK facilitates the phosphorylation / dephosphorylation of creatine
Creatine kinase is a molecule that is predominantly found within the cell, where it performs its function. However, it is possible to find the enzyme circulating in the blood in a range that does not exceed 200 U / L.
Normal CK values can vary based on factors such as age, gender, race, build, and physical activity. In general, in males it is usually slightly higher.
Reference values:
Men: 15 to 180 U / L.
Women: from 10 to 150 U / L.
CK is an enzyme present in muscle cells -both striated and smooth- and the nervous system. Damage to the tissue of these organs involves cell injury, allowing the enzyme to be released into the blood..
There are multiple causes of increased serum creaticinase levels, predominantly muscular, cardiac and cerebral. Other causes are related to factors that influence the alteration of these organs.
Striated muscle can be affected acutely or chronically. Chronic diseases - such as myositis - increase CK levels moderately.
- Trauma.
- Compartment syndrome.
- Parenteral treatment, especially intramuscular or subcutaneous.
- Intense physical exercise.
- Rhabdomyolysis.
- Myosistis.
- Syndromes associated with muscular dystrophy, such as Duchenne disease or Becker muscular dystrophy.
- Acute coronary accidents, such as angina pectoris and myocardial infarction.
- Cardiomyopathies of different causes.
- Infections, in the case of viral myocarditis.
- Heart failure.
- Pericarditis.
- Defibrillation and electrical cardioversion due to intense muscle contraction, with relative cell damage.
Any factor capable of inducing damage to the nervous tissue produces as a consequence elevation of the enzymes in the blood. The CK-BB fraction is the one that is predominantly affected.
- Infections such as meningitis and encephalitis.
- Cerebrovascular disease, especially of the ischemic type (cerebral infarction).
- Brain tumors.
- Cranioencephalic trauma including contusion and cerebral edema.
- Epilepsy and seizures. In this case, the BB and MM fractions may rise, due to the intense muscle contraction..
Certain organic alterations, diseases and external agents can produce high creatine kinase. This is the product of the influence that certain clinical conditions have on tissue and cellular integrity..
Thyroid diseases - including thyroiditis, hypo, and hyperthyroidism - Addison's disease and Cushing's syndrome.
Neoplasms or cancerous tumors, due to their ability to alter and destroy tissues, can cause the release and increase of the enzyme. Examples of this are cancer of the digestive tract, prostate, rhabdomyosarcoma or brain tumors.
Both narcotic drugs, alcohol, cocaine and barbiturates as well as commonly used medications. The latter include cholesterol-lowering drugs (statins), antibiotics, pain relievers, insulin, and sodium heparin. Thyroid hormone supplements can also raise CK values.
It should be noted that some rare diseases are causes of high CK. Some of them are:
- Reye syndrome
- Malignant hyperthermia
- Hemolytic syndromes.
- Neuroleptic malignant syndrome.
Creatine phosphokinase is biologically active in the presence of its substrate creatine. Reactions involving creatine and CK occur within cells. On the other hand, the enzyme found in the blood can be used when required..
CK per se has no biological effects when in free form. However, its presence in amounts above normal is an important indicator of organic damage..
When an injury occurs to the heart muscle, its cells release CK-MB into the bloodstream. The elevation of isoenzymes occurs over several hours. A high MB fraction indicates damage to the myocardium that can cause from a dysfunction of the organ to its total failure.
Elevated CK-MB is related to cardiac pathology and, therefore, arrhythmias, infarction and heart failure are consequences of myocardial injury.
The isozyme found in skeletal muscle is CK-MM, and its elevation in the blood indicates moderate to severe muscle damage..
Rhabdomyolysis - a condition resulting from strenuous physical exercise - causes enzyme elevation and myoglobin release. Rhabdomyolysis is related to renal tubular damage.
Any entity or pathology that affects the central nervous system, both traumatic and infectious, will cause an elevation in the blood of the BB fraction of creatine kinase.
Although it is not a routine analysis, its presence indicates the presence of organic lesion and can even predict its evolution..
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