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Post-synthetic changes in creatine kinase isozymes (EC 2.7.3.2)
Summary
The creatine kinase (CK) MM3 and MB2 isozymes transform into MM1/MM2 and MB1, respectively. This postsynthetic modification, observed in vitro and in vivo, is driven by a thermolabile factor.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Creatine kinase (CK) isozymes (MM, MB, BB) are crucial biomarkers.
- Post-myocardial infarction, CK isozyme patterns in serum undergo significant changes.
- Previous studies noted in vivo shifts from MM3 to MM1/MM2 and MB2 to MB1.
Purpose of the Study:
- To investigate the in vitro conversion of CK MM3 to MM1/MM2 and MB2 to MB1.
- To determine the origin and mechanism of CK isozyme interconversion.
- To establish whether CK isozyme changes are postsynthetic (epigenetic).
Main Methods:
- In vitro incubation of muscle extracts with low-activity serum.
- Analysis of creatine kinase isozyme patterns using electrophoretic techniques.
- Characterization of the factor responsible for isozyme transformation.
Main Results:
- The in vivo observed conversion of MM3 to MM2 and MM1 occurs in vitro.
- A parallel conversion of MB2 to MB1 was detected in vitro.
- MM1, MM2, and MB1 isozymes are absent in muscle cells, indicating postsynthetic modification.
Conclusions:
- The observed creatine kinase MM and MB isozyme patterns are postsynthetic (epigenetic).
- A thermolabile substance facilitates the conversion of MM3 to MM1 via MM2.
- The same mechanism is proposed for the MB isozyme interconversion.