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Mitochondrial creatine kinase (EC 2.7.3.2) in the brain
Abstract:
No CK MM was found in human brain tissue. Both human and rat brain tissue, however, contain a non MM, non BB CK isozyme. The protein is membrane bound. Evidence is presented that it is a mitochondrial variant of the enzyme. This mitochondrial brain CK occurs in two forms. Both a low molecular mass form (Mr = 65,000) and a high molecular mass form are detectable. The isoelectric point of the low molecular mass form, Br-CKm1, is similar to the isoelectric point of CK MM. Complications may arise when techniques are used that try to separate the mitochondrial CK forms from CK MM on basis of differences in net change. The two mitochondrial brain CK forms are called Br-CKm1 and Br-CKm2. Whether these two enzymes are identical to the mitochondrial heart CK forms remains unclear.
Insights
Researchers found a non-MM, non-BB creatine kinase (CK) isozyme in human and rat brain tissue, distinct from brain CK-MM. This membrane-bound enzyme appears to be a mitochondrial variant present in two forms.
Area of Science:
- Biochemistry
- Neuroscience
- Enzymology
Background:
- Creatine kinase (CK) isozymes play crucial roles in cellular energy homeostasis.
- CK-MM is the predominant isozyme in skeletal muscle, while CK-BB is found in the brain.
- Previous studies have not identified CK-MM in human brain tissue.
Purpose of the Study:
- To investigate the presence and characteristics of creatine kinase (CK) isozymes in human and rat brain tissue.
- To identify and characterize a non-MM, non-BB CK isozyme in the brain.
- To determine if this brain-specific CK isozyme is a mitochondrial variant.
Main Methods:
- Analysis of human and rat brain tissue for CK isozyme composition.
- Biochemical assays to characterize the properties of the identified brain CK isozyme.
- Molecular weight and isoelectric point determination.
Main Results:
- No CK-MM was detected in human brain tissue.
- A non-MM, non-BB CK isozyme was identified in both human and rat brain tissue.
- This brain CK isozyme is membrane-bound and appears to be a mitochondrial variant, existing in two forms (Br-CKm1 and Br-CKm2) with different molecular masses.
Conclusions:
- Human and rat brain tissue contain a unique mitochondrial creatine kinase (CK) variant, not CK-MM.
- The low molecular mass form (Br-CKm1) shares similar isoelectric points with CK-MM, potentially complicating separation techniques.
- Further research is needed to ascertain if these mitochondrial brain CK forms are identical to mitochondrial heart CK forms.