Background: The AACC assembled a committee to identify and validate a standard creatine kinase MB isoenzyme (CK-MB) material to improve the comparability of CK-MB mass assays.
Methods: Three protocols were used. In protocol I, various CK-MB materials prepared in different matrices were screened as candidate standards. In protocol II, participating manufacturers calibrated their systems with concentrates of human heart CK-MB and then tested 20 patient samples to evaluate calibration bias. In protocol III, participating manufacturers calibrated their immunoassay systems using recombinant CK-MB2 (rCK-MB2) diluted into their respective sample diluents and measured 50 samples.
Results: Candidate materials showed high recovery in stripped human serum, but bias improved only from 59% to 38%. These data led to the use of human heart CK-MB diluted in each manufacturer’s sample diluent. This strategy reduced bias from 31% to 15%. Because human heart CK-MB is difficult to provide, a lyophilized source of CK-MB2 was identified. rCK-MB2 was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, reversed-phase HPLC, intrinsic protein fluorescence, circular dichroism, agarose gel electrophoresis, immunoreactivity studies, high and low temperature stability, and reconstituted stability to be equivalent to human heart CK-MB. Calibration of immunoassay systems with rCK-MB2 added into each respective manufacturer’s sample diluent showed a 13% between-manufacturer bias.
Conclusion: Lyophilized rCK-MB2 was determined suitable for use as a reference material for CK-MB mass assays.
The purpose of this study was to investigate the kinetic properties of human
creatine kinase (CK) isoenzymes partially purified from heart and skeletal muscle. Utilizing
the backward CK-catalyzed reaction of creatine phosphate + ADP ^ creatine + ATP, K
values for heart and skeletal muscle CK MM (3.7 mmol/1) were significantly (p < 0.05)
greater than CK MB (2.1 mmol/1) which were significantly (p < 0.05) greater than mitochondrial
CK (1.8 mmol/1) at variable creatine phosphate and fixed ADP concentrations. However,
K(m) values for similar isoenzymes from the two different tissues, i.e., CK MB from heart
vs. skeletal muscle, were not different. These results show that kinetic analysis of CK isoenzymes
cannot differentiate the tissue source of elevated blood CK isoenzymes after the acute
stress of long distance running or after acute myocardial infarction.
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