MBC - Creatine kinase Flashcards
What is the purpose of CK?
Catalyses the hydrolysis of creatine phosphate which acts as a buffer for ATP production
What is the reaction for CP hydrolysis?
Creatine phosphate + ADP + H+ —–> Creatine + ATP.
What is the free energy for the hydrolysis of CP?
-43.1 kJ/mol
Where is creatine kinase found?
All cells, but especially high in brain and myocytes
What are the isoenzymes of CK?
MM, BB, MB - all dimers formed from the expression of genes in their respective tissues
Where is BB found?
Brain (brain only expresses B)
Where is MB found?
Myocardium (expresses M and B) - makes up 15% of heart CK
Where is MM found?
Skeletal muscle - skeletal muscle only expresses M
What does CK in the blood mean?
Cell damage or death due to loss of membrane integrity thus membrane leakage
what does BB in the blood mean?
Stroke or death/damage of brain cells
What does MM in the blood mean?
Muscle damage e.g. muscle dystrophy
What does MB in the blood mean?
Myocardial infarction
How do we test for CK
Coupled assay
Outline the test steps for CK detection
- Add CP and ADP to give ATP and C
- Add glucose and hexokinase, if ATP present, we will get G-6-P + ADP
- Add NAD+ and G-6-P dehydrogenase, to give 6-phosphogluconate and NADPH + H+.
- Then use spectrophotometry to detect NADPH - can work out CK levels and see if there was any CK in blood.
How might the three isoenzymes be separated in electrophoresis?
Each dimer is made of up two monomers - either M or B which are two different isoforms. Although they weight the same, they have different isoelectric points (pI), therefore will move differently in electrophoresis.
