[The current aspect of serum creatine kinase in the laboratory medicine].
Two novel immunochemical methods for CK isozyme analysis using monoclonal antibodies were evaluated. One is an immunochemiluminescence method for CK-MB. The other is an immunochemical method for CK-MM isoform. 1) CK-MB: The conventional methods for CK-MB analysis currently used in many laboratories measure enzyme activity, but the immunochemiluminescence method, currently developed, has a completely different principle. By use of a specific monoclonal antibody for CK-MB, it can measure CK-MB as protein dose, including biologically inactive CK-MB. Therefore, we can avoid several error factors in the measurement of CK-MB. This immunochemiluminescence method enables us to observe the true CK-MB behavior in the blood stream. 2) CK-MM isoform: The measurement of fluorescence intensity after electrophoresis is a routine method for the analysis of CK-MM isoform (MM1, MM2, and MM3). Recently a monoclonal antibody against the M-subunit of CK-MM isoform has been developed. This antibody can recognize and inhibit the M-subunit, containing a lysine residue at the C-terminal end. Therefore, the application of the monoclonal antibody enables us to measure quantitatively CK-MM isoform without electrophoresis. 3) CK-MM isoform converting factor: CK-MM3 is converted to MM1 via MM2 in the blood stream. The nature of this converting factor is suspected to be a carboxypeptidase-N, but this has not been confirmed.