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A '''creatina quinase''' ('''CK'''), tamén chamada '''creatina fosfoquinase''' ('''CPK''') ou '''fosfocreatina quinase''', é un [[encima]] ({{EC number|2.7.3.2}}) expresado en varios [[tecido (bioloxía)|trcidos]] e tipos celulares. A CK cataliza a conversión de [[creatina]] e utiliza [[adenosín trifosfato]] (ATP) para crear [[fosfocreatina]] (PCr) e [[adenosín difosfato]] (ADP). Esta reacción encimática da CK é reversible, polo que pode xerarse ATP a partir de PCr e ADP.
En tecidos e células que consomen ATP rapidamente, especialmente o [[músculo esquelético]], pero tamén o [[cerebro]], [[céllacélula fotorreceptora|células fotorreceptoras]] da [[retina]], [[célula pilosaciliada|células pilosasciliadas]] do [[oído interno]], [[espermatozoide]]s e [[músculo liso]], a [[fosfocreatina]] (PCr) serve como reservorio de enerxía para un rápido tamponamento e rexeneración do ATP in situ, así como para o transporte de enerxía intracelular pola lanzadeira ou circuíto da fosfocreatina.<ref name=pmid1731757>{{cite journal | vauthors = Wallimann T, Wyss M, Brdiczka D, Nicolay K, Eppenberger HM | title = Intracellular compartmentation, structure and function of creatine kinase isoenzymes in tissues with high and fluctuating energy demands: the 'phosphocreatine circuit' for cellular energy homeostasis | journal = The Biochemical Journal | volume = 281 ( Pt 1) | issue = 1 | pages = 21–40 | date = January 1992 | pmid = 1731757 | pmc = 1130636 | doi = 10.1042/bj2810021 }}</ref> Así, a creatina [[quinase]] é un importante encima en ditos tecidos.<ref name=pmid7808454>{{cite journal | vauthors = Wallimann T, Hemmer W | title = Creatine kinase in non-muscle tissues and cells | journal = Molecular and Cellular Biochemistry | volume = 133-134 | issue = 1 | pages = 193–220 | year = 1994 | pmid = 7808454 | doi = 10.1007/BF01267955 | eissn = 1573-4919 }}</ref>
ClinicallyClinicamente, creatinea kinasecreatina isquinase assayedutilízase inpara bloodfacer testsprobas asnas aanálises markerde ofsangue damagecomo ofmarcador de danos en tecidos ricos en CK-rich tissuecomo suchos asafectados inpor [[myocardialinfarto infarctionde miocardio]] (heart attack), [[rhabdomyolysisrabdomiólise]] (severegrave muscledegradación breakdownmuscular), [[musculardistrofia dystrophymuscular]], autoimmune [[MyositisMiosite|miosítidos]] [[autoinmunidade|myositidesautoinmunes]], ande [[acutelesión kidneyrenal injuryaguda]].<ref>{{cite journal | vauthors = Moghadam-Kia S, Oddis CV, Aggarwal R | title = Approach to asymptomatic creatine kinase elevation | journal = Cleveland Clinic Journal of Medicine | volume = 83 | issue = 1 | pages = 37–42 | date = January 2016 | pmid = 26760521 | pmc = 4871266 | doi = 10.3949/ccjm.83a.14120 }}</ref>
[[Ficheiro:Creatine kinase rxn.png|500px]]
== Tipos ==
In the cells, the "cytosolic" CK enzymes consist of two subunits, which can be either ''B'' (brain type) or ''M'' (muscle type). There are, therefore, three different [[isoenzyme]]s: CK-MM, CK-BB and CK-MB. The genes for these subunits are located on different [[chromosome]]s: ''B'' on 14q32 and ''M'' on 19q13. In addition to those three ''cytosolic'' CK isoforms, there are two [[mitochondrion|mitochondrial]] creatine kinase isoenzymes, the ''ubiquitous'' and ''sarcomeric'' form. The functional entity of the latter two mitochondrial CK isoforms is an octamer consisting of four dimers each.<ref name=pmid16236486>{{cite journal | vauthors = Schlattner U, Tokarska-Schlattner M, Wallimann T | title = Mitochondrial creatine kinase in human health and disease | journal = Biochimica et Biophysica Acta | volume = 1762 | issue = 2 | pages = 164–80 | date = February 2006 | pmid = 16236486 | doi = 10.1016/j.bbadis.2005.09.004 }}</ref>
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