Isoenzymes pattern

As the acute episode resolves, the MB fraction decreases rapidly and is usually undetectable after 72 hours. Although (mm) remains elevated and the total CK activity may be above the normal range, it is important to recognize that the majority of the MM is also derived from myocardiim. The LD and CK total activities and isoenzyme patterns are frequently normal up to six hours after onset of symptoms. Between 6 and 12 hours postinfarction there is usually an increased LD activity but normal isoenzyme pattern, while (MB) has already appeared. An... 

Escribano, J. et al., SubceUular localization and isoenzyme pattern of peroxidase and polyphenol oxidase in beetroot Beta vulgaris L), J. Agric. Food Chem., 50, 6123,2002. 

All cell-wall extracts contained several PME isoforms differing in their isoelectric points. The isoenzyme patterns changed significantly during cell ageing. 

Perez J, De La Rubia T, Ben Hamman O, And Martinez J (1998) Phanerochaete flavido-alba laccase induction and modification of manganese peroxidase isoenzyme pattern in decolorized olive oil mill wastewaters. Appl Environ Microbiol 64(7) 2726—2729... 

Cornford, P, Evans J, Dodson A, Parsons K, Woolfenden A, Neoptolemos J, Foster CS (1999) Protein kinase C isoenzyme patterns characteristically modulated in early prostate cancer. Am J. Pathol 154 137-144... 

Although H. annosum has an extremely high variation in the isoenzyme pattern of other enzymes, it produced only a single band in the isoelectric focusing experiment of the laccase preparations isolated from more than 60 different strains (20). 

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. 

An example of an enzyme which has different isoenzyme forms is lactate dehydrogenase (LDH) which catalyzes the reversible conversion of pyruvate into lactate in the presence of the coenzyme NADH (see above). LDH is a tetramer of two different types of subunits, called H and M, which have small differences in amino acid sequence. The two subunits can combine randomly with each other, forming five isoenzymes that have the compositions H4, H3M, H2M2, HM3 and M4. The five isoenzymes can be resolved electrophoretically (see Topic B8). M subunits predominate in skeletal muscle and liver, whereas H subunits predominate in the heart. H4 and H3M isoenzymes are found predominantly in the heart and red blood cells H2M2 is found predominantly in the brain and kidney while HM3 and M4 are found predominantly in the liver and skeletal muscle. Thus, the isoenzyme pattern is characteristic of a particular tissue, a factor which is of immense diagnostic importance in medicine. Myocardial infarction, infectious hepatitis and muscle diseases involve cell death of the affected tissue, with release of the cell contents into the blood. As LDH is a soluble, cytosolic protein it is readily released in these conditions. Under normal circumstances there is little LDH in the blood. Therefore the pattern of LDH isoenzymes in the blood is indicative of the tissue that released the isoenzymes and so can be used to diagnose a condition, such as a myocardial infarction, and to monitor the progress of treatment. 

Martinez-Lara, E., Toribio, F., Lopez-Barea, J., and Barcena, J.A., Glutathione S-transferase isoenzyme patterns in the gilthead seabream (Sparus aurata) exposed to environmental contaminants, Comp. Biochem. Physiol, 113C, 215,1996. 

Nixon PF, Kaczmarek MJ, Tate J, Kerr RA, and Price J (1984) An erythrocyte transketo-lase isoenzyme pattern associated with the Wernicke-Korsakoff syndrome. European Journal of Clinical Investigation 14, 278-81. 

White TC, Agabian N Candida albicans secreted aspartyl proteinases Isoenzyme pattern is determined by cell type, and levels are determined by environmental factors. J Bacteriol 1995 177 ... 

The values for the normal leukocyte acid phosphatase activity and the normal isoenzyme pattern will be described in connection with the alteration of these in various hematologic and hematopoietic disorders. 

In one study of patients receiving heparin, the isoenzyme pattern of lactate dehydrogenase was studied all had rises in the hepatic form of the enzyme, suggesting hepatocellular damage as the most likely source (60). 

Fig. (3). Isoenzyme patterns of leaf Vitis vinifera paoxidase separated by isoelectric focusing in 3.5-10.5 pH gradients stained with 4-methoxy-a-naphthol (a) and gallic acid (b) in the presence of H2O2. Arrows indicate peroxidase isoenzymes with high gallic acid oxidizing activity...

Atypical bands in an isoenzyme pattern maybe the result of binding by an immunoglobulin (a macroenzyme). 

The distributions of isoenzymes of aldolase, LD, and CK in the muscles of patients with progressive muscular dystrophy have been found to be similar to those in the earlier stages of development of fetal muscle. The isoenzyme abnormalities in dystrophic muscle have been interpreted as a failure to reach or maintain a normal degree of differentiation. Isoenzyme patterns in regenerating tissues may also show some tendency to approach fetal distributions. This tendency may result from relaxation or modification of control systems in rapidly dividing cells and may account for some of the isoenzyme changes noted (e.g., in muscle in acute polymyositis). 

The isoenzyme patterns of aldolase, pyruvate kinase, and hexosaminidase have also been shown to undergo a change toward fetus-like patterns in hepatoma. 

Hemolysis, if sufficiently severe, produces an LD isoenzyme pattern similar to that in myocardial infarction. Megaloblastic anemias, usually resulting from the deficiency of folate or vitamin cause the erythrocyte precursor cell to break down in the bone marrow (ineffective erythropoiesis), resulting in the release of large quantities of LD-1 and LD-2 isoenzymes. Marked elevations of the total LD activity in serum— up to 50 times the upper reference limit—have been observed in the megaloblastic anemias. These elevations rapidly return to normal after appropriate treatment. 

ALD is a tetramer with subunits determined by three separate gene loci. Only two of these loci, those producing A and B subunits, appear to be active simultaneously in most tissues, so the most common isoenzyme pattern consists of various proportions of the components of a five-member set of isoenzymes, of which two members correspond to the A and B homopolymers. The locus that determines the structure of the C subunit is active in brain tissue, as is the A locus, so this tissue contains ALD A and C together with the three corresponding heteropolymers. 

Isoenzymes. Weber (W3), Grosfield et al. (G15, G16), and Marghescu (M5) have all examined the LDH isoenzyme patterns in normal and psoriatic skin. The pattern in both is that of an anaerobic tissue, i.e., a predominance of the cathodal bands 4 and 5. Psoriatic lesions tend to have increased activity and a slight shift to a more aerobic pattern. 

Considerable interest was aroused by the finding of Wieme and Lauryssens (W16) in 1962 that there is a change in the electrophoretic isoenzyme pattern of lactate dehydrogenase in diseased human muscle. The major isoenzyme of lactate dehydrogenase in most normal muscles moves slowest on electrophoresis (LDH 5), but in myopathic muscle the proportion of LDH 5 may be considerably reduced. This finding has been confirmed and extended by numerous workers, utilizing various techniques for isoenzyme differentiation (e.g., BIO, E5). The abnormal pattern is seen in most, but not all, cases of Duchenne dystrophy and in a variety of other muscular disorders. It may be evident in the very early stages of Duchenne dystrophy (P2) and is seen even in some female carriers of the disease (E3). 

As first pointed out by Dreyfus et al. (Dll), the abnormal LDH isoenzyme pattern in diseased muscle resembles that of normal fetal muscle. In fact, in dystrophic chickens the normal adult isoenzyme pattern is never attained in the affected birds (D3), and possibly this is true of some human muscle diseases. An increase in the specific activity of many other glycolytic enzymes during development has been reported (B5, K3). 

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 ... 

The use of appropriate normal ranges is important in evaluating abnormal levels of plasma enzymes. However, an abnormal isoenzyme pattern may occur despite normal total activity (see above). The standard unit for enzyme activity was discussed in Chapter 6. The normal range is affected by a variety of factors age, sex, race, degree of obesity, pregnancy, alcohol or other drug consumption. 

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