Serum creatine kinase BB linked to immunoglobulin G

Clinical role of recurrently elevated macro creatine kinase type 1

The typical creatine kinase (CK) isoenzymes include CK-BB, CK-MB, and CK-MM. Macro CK type 1, one of the atypical CK enzymes, has been identified in human serum, but the clinical significance still remains uncertain. In our laboratory, 105 patients who expressed serum macro CK isoenzyme type 1 were identified from March 2004 to March 2007. We found that macro CK type 1 recurred after at least one month in 16 patients. Clinical diagnoses were myopathy in 14 patients, sepsis in one, and acute coronary syndrome in one. The averages of serum total CK and macro CK type 1 were 9,132 and 1,925 (U/L), respectively. The linear regression analysis between recurrent macro CK type 1 and total CK revealed a good correlation (y=3.5054x+2381.3, R(2)=0.7822, P<0.001). Three patients had critical illness, including one respiratory failure and two mortalities. Good linear correlation is documented between total CK and recurrent macro CK type 1. In conclusion, the macro CK type I isoenzyme recurred primarily in patients with myopathy.

Macroaspartasemia as a cause of isolated elevation of aspartate aminotransferase--its biochemical and physiological characteristics

OBJECTIVES

The increase of serum aspartate aminotransferase (AST) is generally found in hepatic, cardiac, muscular disease and hemolytic disorders of the red blood cell (RBC). The elevation of its activity is suspected in pathological conditions of these organs. However, instances without any of those conditions rarely exist.

METHODS

The experimental samples were obtained from a normal person's hemolysed RBC, a hepatitis patient and a macroaspartatemic female's serum. They were studied with exclusion chromatography, electrophoresis of AST and changes of AST activity due to Polyethylene Glycol (PEG) and various conditions on storage.

RESULTS

1) The patterns of AST activity by exclusion chromatography are similar to the hemolysed RBC and the hepatitis's serum but differs by the isolated AST elevation. 2) The AST activity with addition of PEG and different anti-immunoglobulin subtypes to different serums are slightly decreased in hepatitis but markedly decreased with PEG and anti-IgG in macroaspartatemia. 3) The patterns of AST activity in electrophoresis are single band-cytosomal AST (cAST)-from hemolysed RBC and two bands-mitochondrial AST (mAST) and cAST-from hepatitis, the major being cAST and the minor mAST. Even though there are two bands, the major one is atypical and the minor corresponds to mAST in macroaspartatemia. 4) The changes of AST activity on storage according to time and temperature show to be stable over 4 weeks at room temperature and cooled condition, and 9 weeks under frozen state in macroaspartatase.

CONCLUSION

Concluding from the above findings, macroaspartatemia is an enzyme-immunoglobulin complex composed of cAST with IgG. MacroAST might be stabler than usual AST at physical conditions.

Electrophoretic analysis of enzyme-linked immunoglobulins and their clinical significance

The appearance of circulating enzyme-linked immunoglobulin complexes (E-Ig) is common for most enzymes used in clinical biochemical tests. The presence of E-Ig may result in altered enzyme activity in serum and interfere with the measurement of isoenzymes, and is thus of diagnostic importance. E-Ig can be identified by confirming that the binding protein is an immunoglobulin by its reaction with specific anti-human immunoglobulin antibodies. Currently, the presence of E-Ig in an individual is regarded as a benign phenomenon, not indicative of any particular disease process. However, it is becoming clear that E-IgG are closely associated with autoimmune states.

Chromatographic and electrophoretic studies of circulating immune complexes in plasma

The protein nature of soluble immune complexes from fresh plasma was studied by combining several analytical biochemical techniques. Free immunoglobulins (Ig) G were separated from larger immune complexes by gel permeation chromatography. In a second step, immune complexes, free IgA and IgM were isolated by protein-A and protein-G affinity chromatography and analysed by two-dimensional gel electrophoresis. Sixteen plasma samples from healthy donors were analysed and evaluated visually. Their protein profiles on the gels turned out to be similar, showing only slight quantitative differences. In one case, additional proteins were detected. To prove the ability of the method, immune complexes were analysed from four plasma samples that showed macro creatine kinase type 1, a complex formation between creatine kinase BB and IgG. This methodology can be used for the examination of immune complexes of unknown protein composition in serum or plasma.

An immunologic pathway for intravascular catabolism of creatine kinase subform MM3

In vitro incubation of the MM3 subform of human creatine kinase (ATP:creatine N-phosphotransferase, EC 2.7.3.2, CK) with fresh human serum resulted in the formation of a complex of high relative molecular mass (Mr 320 kDa). The formed complex (macro CK-MM3) consists of both CK-MM3 and immunoglobulin A (IgA), and its amount of the formed complex was proportional to CK-MM3 activity and IgA concentration. Two molecules of CK-MM3 combined with one molecule of IgA, and the immunoglobulin inhibited the enzyme activity. As IgA does not form complexes with other subforms (CK-MM2 and CK-MM1) or CK-MB, the antigen specificity of IgA to CK-MM3 is definitely exacting. The circumstantial evidence suggests that macro CK-MM3 is a specific antigen-antibody complex. Macro CK-MM3 was detected in all of the examined sera of adult patients with more than 2001 U/1 CK activity (the positive percentage of macro CK-MM3 in all adult patients was 73%), but not detected in sera of patients who were younger than 12 months old. No relationship was observed between macro CK-MM3 and the patients' underlying diseases. Macro CK-MM3 formation suggested to be an immunologic pathway for intravascular catabolism of CK-MM3 when its activity increases.

Enzyme-linked immunoglobulins and their clinical significance

Most of the enzymes used in routine biochemical tests have been detected in circulating enzyme-linked immunoglobulin (Ig) complexes (E-Ig). The complexes often cause unexplained hyperenzymemia and give anomalous patterns on isozyme electrophoresis. However, E-Ig does not appear to be associated with any pathological conditions. The present study was undertaken to determine the clinical characteristics of patients with E-Ig. More than 42,000 patients selected at random and 10,000 blood donors were screened for lactate dehydrogenase (LDH)-linked Ig complexes (LDH-Ig), amylase (Amy)-linked Ig complexes (Amy-Ig), alkaline phosphatase (AP)-linked Ig complexes (AP-Ig) and creatine kinase (CK)-linked Ig complexes (CK-Ig). LDH-Ig and Amy-Ig were screened by electrophoresis for routine isozyme analysis and identified by precipitin reactions. AP-Ig and CK-Ig were screened and identified by counter immunoelectrophoresis. The incidence of all E-Ig ranged from 0.18% to 0.61% in patients and from 0.03% to 0.23% in blood donors. The incidence curves of E-Ig were age-related, generally increasing with age. The curves of E-IgG's for different enzymes resembled each other in shape but those of E-IgA's did not. A positive correlation between E-IgG and autoimmune diseases was present. Consequently, it is concluded that both autoimmune diseases and age are the common clinical factors involved in E-IgG. No specific diseases were found for cases with E-IgA. However, it is suggested that some CK-IgA, but not all, is caused by elevated serum CK activity.

Clinical significance and characteristics of creatine kinase-immunoglobulin complexes in sera from patients with malignant tumors

Creatine kinase (CK, ATP: creatine N-phosphotransferase, EC 2.7.3.2) and immunoglobulin complexes were detected in 27 of 234 (11.5%) patients with malignant tumors. The complexes electrophoresed between CK-MM and the sample application point. The positive rate was significantly higher than rates in patients with benign diseases, or in healthy adults (p less than 0.001). Primary malignancies of the 27 patients were colon 8, gastric 6, pancreatic 4, liver 5, pulmonary 3 and mammary 1. As 22 of the 27 patients had a recurrence or a metastasis and the mortality rate of the positive group 6 mth after the tests was high (85%), most of the 27 patients had advanced tumors. Thus, the CK-immunoglobulin complexes seem to be a prognosticator of patients with advanced tumors. The classes and types of immunoglobulins in the complexes were IgA lambda, 7; IgA kappa lambda, 5; IgA (types of the light chain were not identified), 4; IgA/G kappa, 1; IgA/G lambda, 3; and IgA/G kappa lambda, 7. The molecular sizes of the complexes were 384,000 +/- 22,000 (mean +/- 1 SD). The results of recombination assays using IgA isolated from the complexes of 4 patients suggested that the complexes in the patients' sera were mitochondrial CK-IgA. Non CK-M subunit activities of the positive group were 58 +/- 40 U/l (mean +/- 1 SD) and they were significantly higher than those of the complex negative group of tumor patients (p less than 0.01). This is probably the first report of detection of mitochondrial CK-IgA complexes.

Creatine kinase (CK)-linked IgA in Isaacs' syndrome. An immune complex disease?

Electrophoresis of serum from a patient with Isaacs' syndrome revealed an atypical creatine kinase (CK) isoenzyme pattern which contained an extra band migrating between CK2(MB) and CK3(MM). Immunofixation demonstrated that the extra band was a complex of CK3(MM) and IgA. The presence of this complex seemed to correlate with increased serum CK levels which were associated with the aggravation of symptoms. Immunofluorescence studies on muscle biopsy samples revealed the presence of the complex in the muscle fiber membrane and motor endplate. The existence of CK-linked IgA in an Isaacs' syndrome suggests that an immunological abnormality may play a role in the pathological process of this rare syndrome.

A new creatine kinase found in mitochondrial extracts from malignant liver tissue

A new creatine kinase (CK, ATP: creatine N-phosphotransferase, EC 2.7.3.2) band was found in mitochondrial extracts prepared from malignant liver tissue. By agar gel electrophoresis the new band (CKmLT) migrated between CK-MM and a sample application point. The CK band was not found in mitochondrial extracts of normal liver, cytosolic extracts of normal and malignant liver homogenates. We thus presume that the origin of CKmLT is from mitochondria of malignant liver tumors. CKmLT reacted with anti-mitochondrial CK antibodies so that its antigenicity was similar to that of mitochondrial CK. Physico-chemical characteristics were similar to those of the polymeric form of the normal liver mitochondrial CK (CKmL1); i.e. relative molecular mass (320 000 to 350 000), heat stability, and the behavior in 2 mol/l urea. CKmLT migrated to the CKmL1 and the MM position after long-term storage at -20 degrees C. CKmLT did not demonstrate affinity to concanavalin A, and there was no significant change in the electrophoretic mobility of CKmLT following neuraminidase treatment.

An assay for creatine kinase conversion factor

The M subunits of creatine kinase (CK) isoenzymes, MM and MB, are subject to a postsynthetic modification in serum. As a result of this modification three sub-bands of MM can be identified by agarose electrophoresis, called MM3, MM2 and MM1 in the order of increasing electrophoretic mobility towards the anode. An assay has been developed for the protein, called creatine kinase conversion factor, which catalyses the reaction leading to the sub-bands. The assay is based on the rate of conversion of MM3 to MM2 and MM1. The first order rate constant for the conversion, designated as kc, for sera of 24 apparently healthy adults ranges from 0.0221 to 0.0740 hr-1 with a mean of 0.0392 hr-1 under the conditions of the assay. Temperature and pH dependence of kc have been determined.

The origin of a cathode-migrating creatine kinase found in serum from a cancer patient

The origin of an atypical creatine kinase (CK, ATP:creatine N-phosphotransferase, EC 2.7,3.2) migrating cathodic to the MM position found in the serum of a cancer patient was studied. The electrophoretic mobility of the atypical CK is similar to that of the fast-moving cathodal mitochondrial CK. The relative molecular mass was estimated to be approximately 350000, and was similar to that of the fast-moving cathodal mitochondrial CK. The atypical CK reacted with anti-human mitochondrial CK antibody. It is therefore suggested that the atypical CK is of mitochondrial origin. After incubation in 2 mol/l urea, the enzyme was converted into a new form migrating to the MM position. The conversion was observed in liver mitochondrial CK but not heart mitochondrial CK. The residual CK activity after heating at 56 degrees C for 60 s was 77%, and the apparent Km value for creatine phosphate at 30 degrees C was about 0.27 mmol for the atypical CK. These characteristics were very similar to those of the liver mitochondrial CK, because the data from the enzyme determined at the same time were 75% for residual enzyme activity to heat, and 0.24 mmol for apparent Km value. Therefore liver mitochondria are suggested to be the source of the atypical CK.

Stability of macro creatine kinases and creatine kinase isoenzymes compared: heat inactivation test for determination of thermostable creatine kinases

Creatine kinase isoenzymes showed decreasing thermal stability and increasing lability towards pH changes in the order: MM, MB, and BB. The three isoenzymes exhibited their highest stability between pH 6.5 and 7.0. At 37 degrees C and an almost physiological pH of 7.5 the decay constants were 0.025, 0.164 and 0.580 h-1 (MM, MB, and BB isoenzyme), respectively. In contrast to free creatine kinase BB, immunoglobulin-linked creatine kinase BB (macro creatine kinase BB, type 1 macro creatine kinase) showed a markedly higher stability; this accounts for the persistence of creatine kinase BB activity in macro creatine kinasaemia. In addition we identified a second type of macro creatine kinase in patients' sera, which is also thermostable. A simple heat inactivation test (20 minutes, 45 degrees C, immunoinhibition of the M-subunits) differentiates thermostable macro creatine kinases from thermolabile creatine kinases and thus completes isoenzyme diagnosis.

Macro creatine kinase BB: evidence for specific binding between creatine kinase BB and immunoglobulin G

In the sera of four female patients with proven IgG-linked creatine kinase BB (macro creatine kinase BB) we studied the nature of the binding between creatine kinase isoenzymes and immunoglobulin G. The specificity towards the isoenzyme bound, the recombination of the complex after treatment with acid buffer, the site of the binding between both partners and an apparently monoclonal nature of the immunoglobulin G involved in the complex indicate that a specific antigen-antibody reaction is responsible for the existence of macro creatine kinase BB in the sera investigated.

Three atypical serum creatine kinases in a patient with carcinoma of the colon

Three electrophoretically atypical creatine kinase (CK) bands were found simultaneously in the serum of a patient with terminal carcinoma of the colon. The atypical CKs were found at the cathodal side of CK-MB (CK-X1), at a sample application point (CK-X2), and at the anodal side of CK-MM (CK-X3) on agar plates. Our data seemed to suggest that CK-X1 was predominantly a CK-IgA/beta-lipoprotein complex, CK-X3 was a CK-IgG complex, and CK-X2 was macromolecular, different from both CK-X1 and CK-X3. The light chains of IgA and IgG were both of the lambda type. All native isoenzymes comprising these atypical CKs were identified as MM type. There was no change of the electrophoretic pattern of serum CK isoenzymes throughout the course of the study.

Studies on the sub-banding of creatine kinase MM and the "CK conversion factor"

In serum, the M subunit of creatine kinase (CK) isoenzymes, MM and MB, is modified by a heat labile factor. As a result of the modification three sub-bands of MM and two of MB can be demonstrated by agarose electrophoresis. Normal sera contain MM1 as the dominant sub-band with lesser amounts of MM2 and MM3. Following tissue damage the MM sub-band distribution changes as a result of the increased release of MM, which occurs as MM3. Immediately after coronary bypass surgery MM3 is the dominant sub-band to be replaced by MM2 and in turn by MM1. The factor responsible for the modification of the M subunit, the "CK conversion factor" has been partially purified and its molecular weight determined.

Membrane associated enzyme complexes containing lambda type immunoglobulin A

The properties of the membrane associated enzyme complexes were investigated. The enzyme complexes of alkaline phosphatase, arylamidase, and L-gamma-glutamyltranspeptidase were excluded by gel filtration on Sephadex G-200. The electrophoretic mobility of the enzyme complexes was found to be in the alpha-1 portion and these enzyme activities were immunologically fixed by anti-IgA and anti-light chain lambda antibodies. Heterogeneity in density was observed by density gradient ultracentrifugation. The activities of membrane-associated enzymes were demonstrated in both high (d > 1.21) and low density particles (1.063 < d < 1.21), and the enzyme activities of a high density particle were immunologically fixed by anti-IgA and anti-light chain lambda antibodies. The heterogeneity in density was based on the presence of immunoglobulin A molecule in the complexes. The specificity of the immunoglobulin which was found in the enzyme complexes proved to be exclusively of the alpha heavy chain classes and lambda light chain types respectively. This isotype specificity of immunoglobulin A is similar to the specificity observed in enzyme-linked immunoglobulins, and simple non-specific binding of immunoglobulin and membrane moiety was eliminated. This isotype specificity is of interest in connection with the properties of the circulating autoantibodies.