Creatine kinase-MB isoenzyme

ST79 Chapelle, J.-P. and El Allaf, M. (1990). Automated quantification of creatine kinase MB isoenzyme in serum by radial partition immunoassay, with use of the Stratus analyzer. Clin. Chem. 36, 99-101. 

ST80 Christenson, R.H., Clemmensen, P., Ohman, E.M., Toffaletti, J., Silverman, L.M., Grande, P., Vollmer, R.T. and Wagner, G.S. (1990). Relative increase in creatine kinase-MB isoenzyme during reperfusion after myocardial infarction is method dependent. Clin. Chem. 36, 1444-1449. 

STN2 Anderson, P.H., Stickel, S.A. and Nadkami, S.R. (1991). An evaluation of new calibrators for the creatine kinase MB isoenzyme on the Baxter Stratus. Clin. Chem. 37, 912-913, Abstr. 18. 

Creatine kinase (CK) occurs in high concentrations in the brain, cardiac and skeletal muscle and is elevated in the blood with muscle damage. A rise in CK is seen in acute myocardial infarction but also in other conditions. A more specific marker is creatine kinase MB (CK-MB), which is an isoenzyme of creatine kinase that is more specific for cardiac muscle damage. CK or CK-MB will rise approximately 4 hours after an acute cardiac event and will reach a peak after approximately 24 hours and will remain raised for 3-4 days. 

Q4 Cardiac enzymes are released into the blood following heart muscle damage during a heart attack. Creatine kinase, particularly its MB isoenzyme, is one of the most specific of these enzymes, which reaches a peak 24 hours after infarction. It rises and then falls within the first 72 hours of the heart attack. Aspartate transaminase is also released, but levels of this enzyme can be raised in several other conditions, so it is less specific than creatine kinase MB. Troponin T is also specific for myocardial damage and is raised for approximately two weeks following infarction. Finding a high concentration of these enzymes in a patient s blood therefore supports the evidence obtained from the ECG and confirms that the patient has suffered a myocardial infarction. 

E632 Jensen, A.E., Reikvam, A., NordgSrd, Pedersen, K.G. and Asberg, A. (1990). Diagnostic accuracy of Kodak creatinine kinase MB, Stratus creatine kinase MB, and lactate dehyrogenase isoenzyme 1 in serum after acute myocardial infarction. Clin. Chem. 36, 1847-1848. 

Immunological methods for enzymes, more specifically isoenzymes, such as lactate dehydrogenase-1 (167, 168), mitochondrial aspartate aminotransferase (169), prostatic acid phosphatase (170, 171,172), and creatine kinase-MB (173, 174, 175), have been in use in the clinical laboratory for 10 years. However, the use of the immunological rather than catalytic properties of enzymes has not provided the opportunities for standardization that was anticipated a number of years ago (176, 177, 178). It is only within the last year that a working group on CK-MB mass assay was formed under the auspices of the Standards Committee of the American Association for Clinical Chemistry (AACC). The objective of this working group is to prepare a reference material to calibrate methods that are based on the principle of CK-MB mass measurement. 

New manual and automated method for determining activity of creatine kinase isoenzyme MB by use of dithiothreitol Clinical applications. Clin. Chem. (1975), 1612-1618. 

As an example, consider the separation of the creatine kinase isoenzymes, MM, MB, and BB. Mercer has used classical ion-exchange chromatography (DEAE - Sephadex - A50) for the resolution of these three isoenzymes (44) To speed up the separation and ultimately to allow an automated analysis,... 

The enzyme responsible for this topping-up ATP in active muscle is CK. CK is found in high concentration in muscle cells, both free within the sarcoplasm and also associated with membranes of mitochondria and the sarcoplasmic reticulum. Structurally, creatine kinase is a dimeric enzyme of B and/or M subunits, each of about 40 kDa. Three quaternary structure isoenzyme forms arise CK-MM, CK-BB and CK-MB. The predominant form in all muscles is CK-MM, but cardiac muscle also contains a significant amount of CK-MB and this isoenzyme can be used as a specific marker of myocardial damage (see Case Notes at the end of this chapter). 

Quaternary structure of isoenzymes Many isoenzymes contain different subunits in various combinations. For example, creatine kinase occurs as three isoenzymes. Each isoenzyme is a dimer composed of two polypeptides (called B and M subunits) associated in one of three combinations CK1 = BB, CK2 = MB, and CK3 - MM. Each CK isoenzyme shows a characteristic electrophoretic mobility (see Figure 5.21). 

Correct answer = D. The CK isoenzyme pattern at admission showed elevated MB isozyme, indicating that the patient had experienced a myocardial infarction in the previous 12 to 24 hours. [Note 48 to 64 hours after an infarction, the MB isozyme would have returned to normal values.] On day 2, 12 hours after the cardioconversions, the MB isozyme had decreased, indicating no further damage to the heart. However, the patient showed an increased MM isozyme after cardo-conversion. This suggests damage to muscle, probably a result of the convulsive muscle contractions caused by repeated cardioconversion. Angina is typically the result of transient spasms in the vasculature of the heart, and would not be expected to lead to tissue death that results in elevation in serum creatine kinase. 

The patient, a 63-year-old Caucasian female, was hospitalized on 4 April 2002 though 10 April 2002 for a non-ST segment elevation myocardial infarction (non-Q-wave MI per chart documentation). She had a negative adenosine stress test after the initial event. Her serum cardiac-specific troponin I (cTnl) concentration 24 hours after her onset of chest pain was 1.4 pg/L (upper limit of normal is 0.3 ng/mL), and her creatine kinase (CK) MB level was 12.5 pg/L (upper limit of normal 6.0 ng/mL). Three days post-event her cTnl level was 0.5 pg/L and her CK-MB level was 4.5 pg/L (Fig. 5-1). MB refers to one of the isoenzyme forms of CK found in serum. The form of the enzyme that occurs in brain (BB) does not usually get past the blood-brain barrier and therefore is not normally present in the serum. The MM and MB forms account for almost all of the CK in serum. Skeletal muscle contains mainly MM, with less than 2% of its CK in the MB form. MM is also the predominant myocardial creatine kinase and MB accounts for 10%-20% of creatine kinase in heart muscle. 

Creatine kinase functions as a dimer. The dimer can consist of combinations of two different subunits, M and B. Different cell types produce or express the MM, MB, or BB forms of CK. Although the amino acid composition of the M and B subunit differ, all three dimeric forms can catalyze the reaction described above. Different forms of an enzyme that catalyze the same reaction (such as the MM, MB, and BB forms of CK) are referred to as isoenzymes. 

Likewise, following the repeated infusion of doses of 1000-2000 mg/kg DCLHb daily for 7 days or of 400 mg/kg every 6h for 3 days, the concentrations of AST, lactate dehydrogenase (LDH) and creatine kinase (CK) were elevated in monkeys. Isoenzyme profiles for CK and LDH revealed predominant increases in the MM form of CK and the LD-5 form of LDH. The MM-CK originates predominantly from skeletal muscle and may also derive from the myocardium however, the MB isoenzyme, which emanates only from myocardium, was not elevated. The elevation of LD-5 was also consistent with a skeletal muscle source. 

Salbutamol causes an increase in the activity of the MB isoenzyme of creatine kinase, which has been interpreted as meaning that it might be cardiotoxic (3). 

Chazan R, Tadeusiak W, Jaworski A, Droszcz W. Creatine kinase (CK) and creatine kinase isoenzyme (CK-MB) activity in serum before and after intravenous salbutamol administration of patients with bronchial asthma. Int J Clin Pharmacol Ther Toxicol 1992 30(10) 371-3. 

E620 Hadberg, A., Hassager, C., Hildebrandt, P. and Christiansen, C. (1990). Comparison of two immunoinhibitory methods with agarose gel-electrophoresis for measuring the MB isoenzyme of creatine kinase in serum from cases of suspected myocardial infarction. J. Clin. Chem. Clin. Biochem. 28, 453-458. 

ST77 Bermes, E.W., Kahn, S.E., Jandresici, M.A., Augustine, G. and Khan, I. (1990). Analytical and clinical comparison of four methods for the determination of the MB isoenzyme of creatine kinase. Clin. Chem. 36, 1130, Abstr. 831. 

ST92 Lianidou, E.S., Christopoulos, T.K. and Diamandis, E.P. (1990). Assay of creatine kinase isoenzyme MB in serum with time-resolved immunofluorom-etry. Clin. Chem. 36, 1679-1683. 

Creatine kinase (CK) catalyzes the phosphorylation of creatine by adenosine triphosphate. CK is a dimer consisting of two subunits, M (muscle) and B (brain). There are three isoenzymes, CKl (BB), CK2 (MB), and CK3 (MM). CKl is present in the brain, prostate gland, gastrointestinal tract, lung, bladder, uterus, and placenta. Cardiac muscle has the highest concentration of CK2 (= 20%). CK3 is present in skeletal and cardiac muscles. 

Three cytosolic isoenzymes (CK-3, CK-2, CK-1) and one mitochondrial isoenzyme (CK-Mt) of creatine kinase (CK) (MW 80,000 Da for all 4 isoenzymes) have been identified and are easily separated on agarose and cellulose acetate by electrophoresis (see Chapter 21). Three different genes have been identified that encode for and are specific for CK-M, CK-B, and mitochondrial CK subunits.Although CK-3 (CK-MM) is predominant in both heart and skeletal muscle, CK-2 (CK-MB) has been shown to be more specific for the myocardium, which contains 10% to 20% of its total CK activity as CK-MB, compared with amounts varying from 2% to 5% in skeletal muscle. 

Gerhardt W, Katus H, RavkHde J, Hamm C, Jorgensen PJ, Peheim E, et al. S-Troponin T in suspected ischemic myocardial injury compared with mass catalytic concentrations of S-creatine kinase isoenzyme MB. Clin Chem 1991 37 1405-11. 

The isoenzyme pattern of creatine kinase in normal and diseased muscle has been investigated by several workers. Two subunits are recognized, usually denoted M and B the enzyme is a dimer, hence three forms are possible MM, BB, and the hybrid MB. Most muscles contain largely MM with sometimes a proportion of BB (the latter is characteristic of brain). Normal fetal muscle, however, contains a preponderance of BB (Gil, S3). After denervation, there is a relative decrease in MM (S3). In muscle from patients with fascioscapulohumeral dystrophy and polymyositis there was an increase in MB relative to MM, but a normal ratio was found in Duchenne and limb-girdle dystrophies and in most cases of neurogenic atrophy BB occurred in some cases of myotonic dystrophy (Gll). 

The diagnosis of organ disease is aided by measurement of a number of enzymes characteristic of that tissue or organ. Most tissues have characteristic enzyme patterns (Table 8-2) that may be reflected in the relative serum concentrations of the respective enzymes in disease. The diseased tissue can be further identified by determination of the isoenzyme pattern of one of these enzymes (e.g., lactate dehydrogenase, creatine kinase) in the serum, since many tissues have characteristic isoenzyme distribution patterns for a given enzyme. For example, creatine kinase (CK) is a dimer composed of two subunits, M (for muscle) and B (for brain), that occur in three isoenzyme forms, BB(CKi), MB(CK2) and MM(CK3), which catalyze the reversible phosphorylation of creatine with adenosine triphosphate (ATP) as the phosphate donor ... 

A Glycophase DEAE-CPG column has been used to resolve arylsulfa-tase isoenzymes in serum and in concentrated urine samples from healthy controls, patients with colorectal cancer, and patients with malignant melanoma (B16). Creatine kinase MM and BB isoenzymes in brain and in muscle extracts have been resolved by anion exchange, but the MB isoenzyme was not detected either because of denaturation in the chromatographic process or because of adsorption to the column (KI8). The MB isoenzyme has been successfully detected on a DEAE-Glyco-phase column in the serum of a patient who had suffered a myocardial... 

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