Creatine Kinase

Question 1

Where are CK concentrations particularly high?

Answer 1

1. Muscle cells
2. Brain cells

Question 2

What happens to the CK of damaged/dead cells?

Answer 2

Leaks into blood

Question 3

What reaction does CK catalyse?

Answer 3

Creatine phosphate + ADP + H+ —> Creatine + ATP
- Creatine kinase
- Reversible

Question 4

What are the 3 dimeric isoenzymes of CK?

Answer 4

BB (brain)
MB
MM (muscle)

Question 5

What is special about MB CK?

Answer 5

Only found in cardiac muscle cells
- 15% MB + 85% MM

Question 6

How is CK activity measured?

Answer 6

Coupled enzyme assays (NADPH)

Question 7

What are the 3 reactions involved in determining CK activity?

Answer 7

1. CP + ADP —> C + ATP
   - CK
2. ATP + D-glucose —> ADP + G6P
   - Hexokinase
3. G6P + NADP+ —> 6-PG + H+ + NADPH
   - G6P dehydrogenase (make NADPH)

• Measure NADPH conc

Question 8

How can the 3 isoenzymes be separated and why?

Answer 8

Gel electrophoresis
- Different charges —> BB most -ve and MM most +ve

Question 9

How can you use CK activity to diagnose myocardial damage?

Answer 9

MB CK will increase

Question 10

Which 4 markers can be used to diagnose myocardial damage? (CK’S got Large Calves)

Answer 10

1. CK
2. SGOT (serum glutamate oxaloacetate transaminase)
3. LDH (lactate dehydrogenase)
4. Cardiac troponin (I and T)

Question 10

How long after a myocardial infarction do each of the markers peak in increase?

Answer 10

1. CK —> 1 day (start inc 4-6 hrs)
2. SGOT —> 2 days
3. LDH —> 5 days
4. Cardiac troponin —> 4/5 days (start inc 2 days)

Question 11

Why is the level of MB CK in blood directly proportional to the extent of cell death in the heart?

Answer 11

Myocytes all approx same volume —> release same volume of CK

Question 12

Why is only measuring CK activity in blood not enough to diagnose myocardial infarction?

Answer 12

Must be MB CK

Question 12

Why isn’t electrophoresis used clinically and what could be used instead?

Answer 12

• Too slow
• ELISA test