Macro creatine kinase BB isoenzyme in serum: most likely an antigen-autoantibody complex

Nine sera containing an abnormal creatine kinase BB isoenzyme, "macro CK-BB", were examined. Immunoglobulin precipitation after addition of radiolabelled CK-BB suggested that in eight of the sera the enzyme was linked to an immunoglobulin G. Results obtained with papain-digested and with pepsin-digested IgG suggested that the binding of CK-BB occurred in the antigen-binding region (the "Fab-region") of IgG. Each of the two antigen-binding fragments of IgG, obtained by papain-digestion, were CK-BB specific, since they complexed this isoenzyme equally well when excess CK-MM and CK-MB was added. From Scatchard plots the affinity constant for binding of CK-BB to IgG and the BB-binding capacity of four of the sera was calculated. The affinity constant was high and differed little between the sera (range 0.7 x 10(11)-1.6 x 10(11)1/mol). The BB-binding capacity differed widely (range 21-900 microgram of CK-BB per litre of serum), but in each serum it roughly paralleled the activity of the macro CK-BB complex. The results suggest that in eight of the nine sera examined the BB-binding IgG is an antibody with activity directed towards CK-BB.

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.

Immunoinhibition test for creatine kinase-B subunit: a comparison of monoclonal mouse and polyclonal goat antibodies

We have established several mouse hybridoma cell lines which secrete monoclonal antibodies with creatine kinase M subunit inhibiting capacity. Some of these antibodies are useful tools for the determination of the creatine kinase-B subunit activity (CK-MB test). The monoclonal mouse anti-bodies and the conventional polyclonal goat antibodies were compared.

Macrocreatine kinase in plasma: a cause for a false positive CK-MB immunoinhibition test

The case of a patient with bronchial neoplasm is described. A non-typical form of creatine kinase found in the plasma gave rise to a false positive CK MB test by the immunoinhibition procedure. Electrophoresis on agarose gels beside a normal MM band showed an additional band between the MB and the MM band of a standard mixture. It could be shown by an immunoprecipitation test using precipitating antibodies against CK-MM and CK-BB that the creatine kinase of the abnormal band consists entirely of the MM-type, which after treatment with polyethylene glycol not only became susceptible to inhibiting anti-M antibodies, but also showed the electrophoretic motility of CK-MM. Gel filtration chromatography clearly demonstrated the macromolecular nature of this abnormal creatine kinase.

Observation of a variant creatine kinase isoenzyme in sera and breast tumor cytosols

A variant creatine kinase (CK) isoenzyme was identified in the sera of some patients who had advanced adenocarcinoma of the breast, stomach, and large intestine. A similar variant isoenzyme, together with a high concentration of CK-BB isoenzyme, was identified in some breast tumor cytosols. The variant creatine kinase activity in both sera and tumor cytosols was unaffected by antibodies specific for both the CK-M and DK-B subunits. This indicates that DK-MB isoenzyme determinations are currently best performed by electrophoretic rather than immunologic technics.

Association of creatine phosphokinase with the cytoskeleton of cultured mammalian cells

Using an antibody specific for creatine phosphokinase (CPK), we have discovered an association between that enzyme and the cytoskeleton. Immunofluorescence observations show that CPK is associated with intermediate filaments in PTK cells and BALB/3T3 cells. The CPK distribution also follows intermediate filaments when cells are treated with colchicine.

Purification of canine myocardial mitochondrial creatine kinase

Mitochondrial creatine kinase, purified for the first time, is a dimeric molecule with a mol. wt of 82,000 and does not hybridize with M or B subunits or react to their specific antiserum. A specific antiserum to the mitochondrial form was developed which does not cross-react with the B or M subunits. Thus, the mitochondrial form is biochemically and immunologically unique.

Purification of mitochondrial creatine kinase. Biochemical and immunological characterization

Mitochondrial creatine kinase was purified from canine myocardium. The preparation exhibited a positively charged isoenzyme free of other creatine kinase isoenzymes and on sodium dodecyl sulfate gel exhibited a single protein band. Amino acid composition showed mitochondrial creatine kinase to be different from that of MM or BB creatine kinase and did not hybridize with the M or B subunits of the cytosolic forms. Antiserum was developed to mitochondrial creatine kinase which did not cross-react with cytosolic creatine kinases. Antiserum to cytosolic creatine kinase exhibited no reaction to mitochondrial creatine kinase. Utilizing the specific antiserum, a radioimmunoassay was developed for the specific detection of mitochondrial creatine kinase. Thus, mitochondrial creatine kinase was purified and shown to be comprised of a unique subunit which is biochemically and immunologically distinct from the cytosolic creatine kinases.

[High levels of CK and its isoenzymes produced by a thymus carcinoma (author's transl)]

A 63 years old female is described suffering from thymus carcinoma with increased levels of CK and CK-MB enzymes. The separation of the total CK enzymes into the isoenzymes CK-MM, CK-BB, and CK-MB showed a marked difference between the photometric and the immunological method. This discrepancy can be explained by postulating a molecule specific for thymus carcinoma, probably a new CK isoenzyme. The relevance of using the photometric method in cardiologic routine diagnostic is pointed out.

Creatine kinase B-subunit activity in serum after immunoinhibition of M-subunit activity

Creatine kinase (EC 2.7.3.2) B-subunit activity in serum may be routinely measured as residual activity after specific immunoinhibition of the M-subunit. We assessed the inhibition kinetics, specificity, completeness of inhibition, and inhibitory capacity of three different anti-M preparations, with use of isolated human BB, MM, and MB isoenzymes. The Scandinavian-recommended reaction system was used. We suggest a set of tentative quality requirements for anti-M for use in diagnosing acute myocardial infarction. The need to measure and subtract sample residual adenylate kinase activity was demosntrated. We describe a routine photometric method for determining B-subunit activity in serum. With the Scandinavian CK method the upper reference value for total creatine kinase in serum was found to be 150 U/L for women, 270 U/L for men. By bioluminescence, we found the upper reference value for B-subunit activity to be 6 U/L for both sexes. We discuss three different modes for applying B-subunit determinations to the diagnosis of acute myocardial infarction.

Creatine kinase forms in human skeletal and cardiac muscle

The creatine kinase (CK) activity in human skeletal and cardiac muscle submitted to QAE-Sephadex chromatography was found to distribute into three peaks (m and h I, II, III fractions). Characterization according to electrophoretic behaviour, approximate molecular weight, thermal stability and immunological properties unambiguously demonstrated the coincidence of fractions I and III with reference MM-CK and MB-CK isoenzymes, while both cardiac and muscular forms II proved to escape any assignment within the dimeric (M, B) model. A higher molecular weight than for reference CK and the absence of interaction with BB-antiserum resulted for both forms II, which on the contrary were found to diverge as for reactivity to MM-antiserum and stability characteristics. Quantitation of the CK forms, attempted on a limited number of samples, confirmed the expected relative levels of MM-CK and BB-CK and gave evidence for the presence of hII- or mII-CK amounting up to 30% of the total activity in cardiac and skeletal muscle, respectively. The results of the study both confirm a complexity greater than supposed for the CK system and point to the inadequacy of several of the commonly used analytical approaches to derive correct information.

[Interaction of human creatine phosphokinase isoenzymes with rabbit antibodies and their Fab-fragments]

The interaction of human creatine phosphokinase isoenzymes with rabbit antibodies and their Fab has been studied. It has been shown that Fab of the antibodies against MM or BB isoenzymes preserve high specificity of intact antibodies and the ability to inhibit creatine kinase isoenzymes. Differences between antibodies and their Fab have been found to exist with respect to the kinetics of binding with homologous isoenzymes: the rate of the complex formation for Fab is significantly higher. The interaction of creatine kinase isoenzymes with intact antibodies and their Fab is not affected by the addition of creatine kinase substrates. The antibodies against MM and BB isoenzymes have been used to study the individual properties of each subunit of the M- and B-type in a hybrid dimer MB. It has been shown that such properties of these subunits as the Michaelis constants, pH dependence and inhibition by homologous antibodies are identical to those of non-hybrid MM and BB isoenzymes, respectively.

Monovalent antibodies against MM-creatine kinase remove the M line from myofibrils

Column-purified antibodies against creatine kinase (EC 2.7.3.2) from chicken skeletal muscle (the homodimeric isoenzyme designated MM-CK) bind specifically to the M lines of chicken pectoral muscle myofibrils. Incubation of myofibrils with monovalent Fab' fragments of these antibodies solubilizes most of the myofibril-bound creatine kinase, concomitantly removing most of the electron-dense material from the M lines. This strongly indicates that MM-CK is an integral part of the M-line structure and is consistent with the suggestion that MM-CK molecules form the M bridges that are responsible for the principle M-line substriations.

Comparison of CK-MB fractionation by antibody inhibition reaction and DEAE-sephadex chromatography

1. CK-MB isoenzyme fractionation has been compared between DEAE-sephadex chromatography and the CK-M-subunit inhibiting antibody procedure. 2. It was found that the inhibiting antibody method generally gave lower values than the chromatography procedure. 3. The above difference can be partially attributed to inhibitory factors in the antibody system. 4. It was concluded that although there was general agreement between the two procedures, the CK-M-subunit inhibiting antibody procedure should be viewed with caution at low creatine kinase activities, and should never be done without the appropriate reagent blanks.

Sensitive assay of creatine kinase isoenzymes in human serum using M subunit inhibiting antibody and firefly luciferase

A sensitive method for the assay of B subunit and total creatine kinase activity is described. The ATP formation in the creatine kinase reaction is continuously monitored by measuring the bioluminescence obtained with a purified firefly luciferase reagent. The B subunit activity is determined using an M subunit inhibiting antibody resulting in greater than 99.5% and approximately 50% inhibition of MM and MB isoenzymes, respectively. The bioluminescent method correlated well with a similar spectrophotometric method in the assay of B subunit as well as total creatine kinase activity (r greater than or equal to 0.98). However, the bioluminescent assay is considerably more sensitive, allowing the assay of B subunit activity in serum from healthy individuals. This is due to the inherent sensitivity of the bioluminescent assay of ATP, a reduced analytical interference from adenylate kinase and a reduced reagent blank. The within-series precision at 1 U/liter and greater than 52 U/liter corresponded to a C.V. of 14% and 3%, respectively. The method is as rapid and suitable for routine work as spectrophotometric methods. From a clinical point of view the new method is of particular interest in the early diagnosis of small acute myocardial infarctions.

Electrophoretic identification of the brain isoenzyme of creatine kinase following treatment with anti-BB antisera

A procedure is described for accurately determining the presence of true creatine kinase isoenzyme BB by fluorescent staining following electrophoresis on either cellulose acetate or agarose. Treatment of sera with anti-BB inhibiting antibody prior to electrophoresis and subsequent enzymatic staining allows clear identification of creatine kinase BB in presence of interfering artifacts. The utilization of an immunological means of identifying BB following electrophoresis avoids the pitfall of associating an artifactual BB isoenzyme with a disease state. Using this technique, presence of creatine kinase BB in patients with carcinoma, cardiac disease and renal failure has been verified.

Radioimmunoassay for subunit B in isoenzymes CK-MB and CK-BB of creatine phosphokinase

We report the development of a double-antibody system for radioimmunoassay of CK-B subunit in isoenzymes CK-MB and CK-BB of creatine phosphokinase. With our method, 4.1 ng/ml of isoenzyme CK-BB can be detected. Within-run and between-run coefficients of variation are respectively 5.3% and 19.6% Analytical recovery of added antigen is 98.9 +/- 14.7%. The CK-B concentration in sera from 20 healthy adults was less than 75 ng/ml. In sera from 25 patients with a rise in CK-total activity, but without CK-MB or CK-BB activity tested with the previous reported immunological methods, we found CK-B concentrations in the range 0--86 ng/ml. In contrast, in 23 sera from patients with acute myocardial infarction within the last 48 hours CK-B concentration was in the range 104--225 ng/ml.