Creatine kinase isoenzymes

Creatine kinase (CK), a widely distributed enzyme in the body, has its highest activities in skeletal muscle and myocardium; when serum CK activities are abnormally increased, injury to these organs must be part of the differential diagnosis. The isoenzyme CK-MB is the most important biochemical test in the diagnosis of acute myocardial infarction.     

Creatine kinase isoenzymes in human cerebrospinal fluid and brain

Extracts of normal brains obtained at autopsy and cerebrospinal fluid (CSF) from patients with global brain ischemia were analyzed for creatine kinase (CK; EC 2.7.3.2) isoenzymes. We used both qualitative and quantitative assays (electrophoresis and immunoinhibition). Brain extracts contained CK-BB isoenzyme and mitochondrial CK. In 54 CSF samples free of blood contamination and with total activities ranging from 7 to 2010 U/L (mean 202 U/L), virtually all of the CK activity was due to CK-BB, and none to CK-MM or CK-MB. We conclude that brain contains CK-BB and mitochondrial CK, but lacks CK-MM and CK-MB. After cardiac arrest, CK-BB is released into the CSF. Any CK-MM in the CSF is probably from blood contamination, in which case immunoinhibition with anti-CK-M antibodies accurately quantifies CK-BB.     

Creatine kinase isoenzymes in serum from children--especially focusing on CK-BB

In 161 children with ages ranging from 7 months to 18 years the concentration of CK-BB in serum was measurable in 58%. The activity in serum of CK-BB (cCK-BB(S] in children varies with age and is not significantly influenced by seizure, epilepsy or body temperature. The values are most elevated during the first year of life and show a rapid fall, never reaching adult levels. Comparing mean cCK-BB(S) values in children to growth charts the resemblance is striking. CK-BB is the only CK-isoenzyme that changes with age. We postulate that cCK-BB(S) is related to growth as a physiological phenomenon. CK-MB was found in serum in 7% of the children and could not be of cardiac origin. Therefore CK-MB cannot be regarded as cardiac specific in children.     

Creatine kinase and lactate dehydrogenase isoenzymes in stage D prostatic carcinoma

Serum creatine kinase (CK) and lactate dehydrogenase (LD) isoenzymes were determined electrophoretically, along with various other biochemical markers of malignancy, in 19 patients with metastatic carcinoma of the prostate. Mitochondrial CK appeared in 15 patients, the CK-BB isoenzyme in 6. As a result, CK activity not inhibited by anti-M-subunit antibodies, CK non-M, was above the reference value in altogether 17 patients. There was a cathodic shift among the LD isoenzymes, significantly more prominent with increasing total LD, and a positive correlation between elevations of CK non-M and LD-5, suggesting a relation to tumour burden for both. An LD 'flip' (LD-1 greater than LD-2) was present in 10/15 patients. The frequency of CK non-M elevations was similar to--but not quantitatively correlated with--elevations of prostatic acid phosphatase and alkaline phosphatase. Thus, changes in CK and LD patterns are frequent in patients with prostatic cancer and must be taken into consideration when acute cardiac symptoms are evaluated in such patients.     

Creatine kinase isoenzymes in the diagnosis of acute cranio-cerebral trauma

The cerebrospinal fluid (CSF) creatine kinase (CK) activity and isozymic spectrum (EC 2.7.3.2) have been examined in patients with craniocerebral injuries of varying severity. The CK activity has been elevated in all the patients. Three isoforms have been detected: CK-BB, CK-MB, and CK-MM. CK-BB has been detected in all the patients in the presence of the total CK activity; this is explained by the isozyme release from the brain tissue during the injury and as a result of functional and structural impairment of the cellular membranes in intensification of lipid peroxidation. The CK-MM activity is due to blood admixture in the CSF and to impaired hematoencephalic barrier during the injury. The presence of CK-MB in the CSF of patients without cardiac symptoms probably results from a recombination of CK-BB and CK-MM isoforms and is of no diagnostic significance. Measurements of the total and isozymic CK activity in the CSF of patients with craniocerebral injuries may become a test for the laboratory diagnosis of the trauma severity and course.     

Creatine kinase isoenzymes of mitochondrial origin in human serum.

We measured creatine kinase (EC 2.7.3.2) activity in 1009 serum samples from 538 patients in the intensive-care units of the University of Texas Medical Branch hospitals. Creatine kinase isoenzymes migrating cathodal to skeletal muscle creatine kinase (CK-MM) on cellulose acetate electrophoresis were found in sera from 14 of the 538 patients. Creatine kinase, lactate dehydrogenase (EC 1.1.1.27), aspartate aminotransferase (EC 2.6.1.1), and alanine aminotransferase (EC 2.6.1.2) activities were abnormally increased in these 14 patients. Liver lactate dehydrogenase isoenzyme (LDH5) and cardiac creatine kinase isoenzyme (CK-MB) were abnormally increased in 12 and eight of these patients, respectively. Ten of the 14 patients died during their hospital admission. We believe the creatine kinase isoenzymes that migrated cathodal to skeletal muscle creatine kinase (CK-MM) were of mitochondrial origin.     

Creatine kinase isoenzymes in extracts of various human skeletal muscles

We have attempted to "map" creatine kinase (CK; EC 2.7.3.2) anatomically by assaying biopsy specimens of skeletal muscles taken from different locations from 109 surgical patients. Substantial activities of CK-MM were present in every specimen; CK-MB was observed in about 44% of these, at approximately 1 to 6% of the total CK activity.     

Creatine kinase isoforms in ischemic heart disease

The MM and MB isoenzymes of creatine kinase exist in serum as a collection of at least three major MM and two major MB isoforms. Each of these are derived from single tissue MM and MB isoforms, which are converted to these other forms by carboxypeptidase N after their release from necrotic skeletal and myocardial tissue. Measurement of the MM isoforms in ischemic heart disease is useful for early diagnosis of acute myocardial infarction and for the noninvasive determination of coronary artery reperfusion for infarction patients receiving thrombolytic therapy. Because MM is also released in acute skeletal-muscle disease, MB isoform measurements may have the highest clinical sensitivity. These determinations are important for providing objective information to cardiologists who need to make critical decisions concerning the management of these patients. I review the procedures for treating patients with myocardial infarction, the potential role of CK isoforms, and the methods currently available for isoform analysis, including high-resolution electrophoresis, isoelectric and chromatofocusing, and liquid chromatography. Rapid and highly sensitive methods are needed for implementation of CK-MM and MB isoforms for prospective emergency determinations for patients with acute myocardial infarction.     

Creatine kinase and lactate dehydrogenase isoenzymes in serum and tissues of patients with stomach adenocarcinoma

Total activities of creatine kinase (EC 2.7.3.2; CK) and lactate dehydrogenase (EC 1.1.1.27; LD) and their isoenzymes were estimated in serum and tissue samples from patients with stomach adenocarcinomas who were to undergo gastric resection. Total CK activity (U/g protein) appeared to be markedly decreased in neoplastic stomach tissue. CK-BB was the predominant isoenzyme in both neoplastic and normal stomach tissues; however, the CK-BB/total CK ratio was increased in adenocarcinoma tissue. Macro CK type 1 was found in two neoplastic tissues and macro CK type 2 in 11. LD4 and LD5 isoenzymes were predominant in gastric tissues, but LD5 and the LD5/LD1 ratio were higher in adenocarcinoma tissue. At 24 h before surgery, CK-BB was demonstrated in sera of all patients and CK-MB in 69%. The CK-BB probably originated from neoplastic stomach tissue, which contains high CK activity, with BB isoenzyme predominating. After gastrectomy, CK and LD isoenzymes in sera were markedly increased by 24 h postsurgery. These alterations were attributed to release from damaged tissue during gastric resection.     

Creatine kinase in serum: 4. Differences in substrate affinity among the isoenzymes

The goal of this work was to find out whether it is possible to measure all three creatine kinase isoenzymes under the same reaction conditions in spite of their different kinetic properties. We found the tightest substrate binding for purified human BB, followed by the MB And MM isoenzyme preparations for both creatine phosphate and ADP. An increase in substrate concentration usually resulted in an inhibition. Nevertheless, it was possible with a method optimized for the MM isoenzyme also to measure the BB and MB isoenzymes at a rate of inhibition of only 6 and 3%, respectively. Marked differences in the apparent Km values between purified and native MM isoenzyme in human serum may indicate that the enzyme declined in substrate affinity during the isolation procedure. The use of enzyme preparations for standardization purposes, therefore, is only suitable if their kinetic properties are close to those of the enzyme in serum. Difficulties in the calculation of the apparent Km values are discussed and the graphical procedures of Lineweaver and Burk and of Eisenthal and Cornish-Bowden compared.     

Creatine kinase (EC-No.2.7.3.2) and creatine kinase isoenzymes during pregnancy and labor and in the cord blood

Total CK and CK isoenzyme activity in serum was investigated during pregnancy, labor and after delivery as well as in cord blood. Total CK was decreased in the second trimester of pregnancy but increased in late pregnancy. Low CK-MB activity in serum was found in patients with early labor pains. CK-BB activity could never be detected during pregnancy. Total CK and isoenzyme activity increased after delivery. The rise of total CK and CK-MB in maternal serum is directly correlated with the following: type of delivery, duration of labor, parity of the mother, and birth weight. From this it can be deduced that postpartum CK levels depend on skeletal muscle activity as well as on the activity of uterine muscle. Prematures and infants "small for date" have significantly lower total CK and slightly more elevated CK-BB activity in cord blood than children of normal maturity. CK-BB activity is much more pronounced in high risk patients with low Apgar score.     

Creatine kinase and lactate dehydrogenase isoenzymes in serum of patients suffering burns, blunt trauma, or myocardial infarction

Medical records of 53 burn and trauma patients were reviewed to assess the possibility of myocardial damage. Except for electrophoretically detectable creatine kinase MB isoenzyme, none showed evidence of myocardial injury. Lactate dehydrogenase isoenzyme tests, electrocardiograms, myocardial pyrophosphate scans, clinical course, and results of (two) autopsies were all negative for myocardial necrosis or ischemia. Types of patient, number, mean peak value (U/L) for serum creatine kinase, and ranges of percentage MB isoenzyme were as follows. Burns from direct electrical contact: 28, 16 600, 0-29; electrical flash or other thermal burns: 10, 4340, 0-22; blunt trauma (mostly from automobile accidents): 15, 3430, 0-18; myocardial infarction: 57, 1520, 4-46. Evidently creatine kinase MB isoenzyme is nonspecific in burn and trauma patients and should not be the only test result used to assess myocardial involvement.     

Creatine kinase and myoglobin determination in myocardial infarction

Summary In order to evaluate the diagnostic and prognostic impertance of serum myoglobin (Mb) determination during acute myocardial infarction (AMI) we determined the time of first rise of both CK and Mb, that is the time in hours between the onset of pain and the last normal myoglobin and enzyme determination (TFR for Mb=2.2±1.5 h; TFR for CK=4.0±2.5 h). We also attempted to evaluate infarct size by mathematical analysis of the serum concentrations of Mb. The average percentage difference between the infarct size calculated from the CK concentrations and Mb concentrations was 35.8±35.2%. The results show that the determination of serum myoglobin is a useful and sensitive test for the early diagnosis of AMI. On the other hand, the serum myoglobin cannot be utilized to evaluate infarct size. The main limitation in the determination of infarct size from the serum Mb concentrations lies in the extreme variability of the disappearance rate (Kd), mainly resulting from the renal elimination of the substance.     

Creatine kinase isoenzyme--antibody reactions in immuno-inhibition and immunonephelometry

I have raised, in rabbits, antibodies against MM and BB isoenzymes of creatine kinase. The antibodies produced were homogeneous by Ouchterlony double immunodiffusion and did not cross react with their opposite antigens. Both antisera, however, appeared to be mixtures of antibodies, displaying different equivalences for activation, inactivation, and, possibly, precipitation. Inactivation studies indicated the presence of antibodies effective against dimer only and antibodies effective against monomer or dimer. Both antisera cross reacted with MB and displayed antibodies that appeared to block only half of the activity as well as antibodies that blocked all of the activity. The antisera produced were useful for measuring MB by both immuno-inhibition and immunonephelometry, but neither appears to be advantageous over current electrophoresis or ion-exchange methods. A comparison of decay of MB in patients between activity and mass measurements indicated that activity decay is about 12-fold faster than mass decay.