2 - Creatine Kinase and Myocardial Infarction

Question 1

Give the reaction that creatine kinase catalyses?

Answer 1

creatine phosphate —–> creatine

Question 2

In what tissues is CK present in high levels?

Answer 2

brain and (skeletal) muscles

NOTE: creatine kinase is present in all cells at low concentrations

Question 3

What are the 2 subunits of CK and what are the different isoforms?

Answer 3

B and M subunits

• muscle = MM
• brain = BB
• Myocardium = BM - the only cells that express both genes and make dimers of the BM form

Question 4

When and why is CK found in the blood?

Answer 4

damage to the cell membrane allows leakage of CK into the bloodstream

Question 5

What, other than damage, can cause the myocardial cells to become leaky?

Answer 5

active transport pumps stop working (lack of ATP)
high concs of solutes build up inside the cell
leaks out

Question 6

How is CK activity determined?

Answer 6

coupled assays are used - uses 2 or more reactions to find something detectable
(creatine and creatine phosphate are not easily detectable)

Question 7

What molecule is dented in a coupled assay for CK?

Answer 7

NADPH

Question 8

How can the 3 isoenzymes be separated?

Answer 8

(similar molecular weight) split based in charge

isoelectric focussing - is a quicker way to do it.

Question 9

How can levels of CK be used to diagnose a myocardial infarction?

Answer 9

look for elevated levels of MB creatine kinase in the serum

NOTE: the levels of BM CK in the serum is directly proportional to the size of the myocardial damage