Creatine kinase other muscle enzymes

The answer b 2 ff VA 2 c (2) (e)). Muscle necrosis irxluced by ionophore toxicosb causes the moiferateto massive release of creatine kinase, a musde enzyme. Levek of the other enzymes [lactate dehydrogenase (LDH) and alkaline phosphatase (AP)) may be moderately or mildly efevated. caldum and... 

In addition to actin and myosin, other proteins are found in the two sets of filaments. Tropomyosin and a complex of three subunits collectively called troponin are present in the thin filaments and play an important role in the regulation of muscle contraction. Although the proteins constituting the M and the Z bands have not been fully characterized, they include a-actinin and desmin as well as the enzyme creatine kinase, together with other proteins. A continuous elastic network of proteins, such as connectin, surround the actin and myosin filaments, providing muscle with a parallel passive elastic element. Actin forms the backbone of the thin filaments [4]. The thin... 

Phosphocreatine (Fig. 13-5), also called creatine phosphate, serves as a ready source of phosphoryl groups for the quick synthesis of ATP from ADP. The phosphocreatine (PCr) concentration in skeletal muscle is approximately 30 nra, nearly ten times the concentration of ATP, and in other tissues such as smooth muscle, brain, and kidney [PCr] is 5 to 10 mM. The enzyme creatine kinase catalyzes the reversible reaction... 

Reasons for the presence of enzymes in the plasma Enzymes can normally be found in the plasma either because they were specifically secreted to fulfill a function in the blood, or because they were released by dead or damaged cells. Many diseases that cause tissue damage result in an increased release of intracellular enzymes into the plasma. The activities of many of these enzymes (for example, creatine kinase, lactate dehydrogenase, and alanine aminotransferase) are routinely determined for diagnostic purposes in diseases of the heart, liver, skeletal muscle, and other tissues. 

Both aspartate aminotransferase and alanine aminotransferase are released into the blood after damage to tissues or after cell death. Consequently, they are used as diagnostic tools when heart or liver damage has occurred, such as after a heart attack or in hepatitis, respectively. Other enzymes are also released into the blood at such times. For example, damage to heart muscle is further characterized by the presence of isoenzymes of creatine kinase or lactate dehydrogenase in the plasma. 

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. 

Blood enzyme tests can detect the abnormalities associated with progressive muscular dystrophy early on, even before symptoms are clearly evident. Muscle tissue is rich in creatine and, when muscles are diseased, the creatine leaks into the blood and can be measured as creatine kinase (CK). The normal level of CK is about 160 lU/L, but an individual with Duchene muscular dystrophy may have CK levels as high as 15,000-35,000 lU/L. If the diagnosis is in doubt, genetic studies and muscle biopsy can also be done. The recent isolation of the Duchenne gene and the discovery that dystrophin is the abnormal encoded protein makes a precise molecular diagnosis possible. It also offers hope that the genetic basis for other dystrophies will be discovered soon. 

There is an increase in serum creatine kinase concentration and electromyography abnormalities. Other serum enzymes, such as the alanine transaminase, aspartate transaminase, and lactate dehydrogenase, also may be increased. Muscle biopsies show a necrotizing inflammatory process. The skin lesions of dermatomyositis show an immune-complex-mediated necrosis of the microvasculature. PM... 

Interruption of the heart s blood supply leads to the death of cardiac muscle cells. The symptoms of myocardial infarction include pain in the left side of the chest that may radiate to the neck, left shoulder, and arm, and irregular breathing. The initial diagnosis is based on these and other symptoms. Therapy is instituted immediately. Physicians then use several enzyme assays to confirm the diagnosis and to monitor the course of treatment. The enzymes most commonly assayed are creatine kinase (CK) and lactate dehydrogenase (LDH). Each enzyme s activity shows a characteristic time profile in terms of its release from damaged cardiac muscle cells and rate of clearance from blood (Figure 6A). 

Proteins that differ somewhat in primary structure and properties from tissue to tissue, but retain essentially the same function, are called tissue-specific isoforms or isozymes. The enzyme creatine kinase is an example of a protein that exists as tissue-specific isozymes, each composed of two subunits with 60 to 72% sequence homology. Of the two creatine kinases that bind to the muscle sarcomere, the M form is produced in skeletal muscle, and the B polypeptide chains are produced in the brain. The protein comprises two subunits, and skeletal muscle therefore produces an MM creatine kinase, and the brain produces a BB form. The heart produces both types of chains and therefore forms a heterodimer, MB, as well as an MM dimer. Two more creatine kinase isozymes are found in mitochondria, a heart mitochondrial creatine kinase, and the universal isoform found in other tissues. (In general, most proteins present in both the mitochondria and cytosol will be present as different isoforms.) The advantage conferred on different tissues by having their own isoform of creatine kinase is unknown. However, tissue-specific isozymes such as MB creatine kinase are useful in diagnosing sites of tissue injury and cell death. 

Creatine kinase (CK or CPK) is one of these enzymes. The protein is composed of two subunits, which may be either of the muscle (M) or the brain (B) type. The MB form, containing one M and one B subunit, is found primarily in cardiac muscle. It can be separated electrophoretically from other CK isozymes and the amount in the blood used to determine if a myocardial infarction has occurred. On admission to the hospital, Ann Jeina s total CK was 182 units/L (reference range 5 38-174 U/L). Her MB fraction was 6.8% (reference range 5% or less of the total CK). Although these values are only slightly elevated, they are typical of the phase immediately following a myocardial infarction. Additional information was provided by myoglobin and troponin T (Tn-T) measurements. 

The reaction is catalysed by arginine kinase (EC 2.7.3 3) (Rg.). There are several other invertebrate R, particularly in worms, e.g. lombricine phosphate and taurocyamine phosphate. The P. of vertebrate muscle is creatine phosphate (phosphocreatine M, 211.1), which is formed from creatine and ATP by the action of creatine kinase (EC 2.7.3.2) (Lohmann reaction. Fig.) reversal of the reaction regenerates ATP. The system, creatine phosphate creatine kinase + ADP, is often used in vitro for the continual generation of ATP, if the enzyme under investigation is inhibited by substrate levels of ATP. 

Musculoskeletal A 69-year-old man with HIV infection developed rhabdomyolysis after taking raltegravir-containing HAART for 2 months, when he started to have progressively worse muscle pain and weakness and could not exercise [140 ]. The creatine kinase activity was 6237 IU/1 and his Uver enzyme was also raised. He stopped taking raltegravir and after 2 days all the enz5mie activities started to fall he recovered fuUy within 1 month. Other reports of rhabdomyolysis have appeared [141, in one case complicated by severe acute renal failure in a 44-year-old man [142 ]. 

An 85-year-old woman with a schizoaffective disorder was given valproate 600 mg/day and after 4 days complained of muscle pain and weakness. Other medications were quetiapine 200 mg/day, nifedipine 10 mg/day, torsemide 10 mg/day, levothyroxine 75 micrograms/day, and acetylsalicylic acid 100 mg/day. There was a fivefold increase in myoglobin concentration (292 ig/l), a sixfold increase in creatine kinase activity (14 pmol/l), and slightly increased liver enzyme activities. The serum... 

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