Creatine Kinase Flashcards
(35 cards)
What is creatine kinase used for?
To convert creatine phosphate into Creatine and ATP
What is delta G hydrolysis of ATP and creatine phosphate?
-31kJ/mole for ATP and -43.1kJ/mole for creatine phosphate
What is a blood test for usually, creatine phosphate, creatine or creatine kinase?
creatine kinase
Where in the body is creatine kinase found in particularly high concentrations?
in the brain and muscle cells
When is creatine kinase released into the circulation?
Following death / damage of brain and muscle cells
How many isoforms are there of creatine kinase?
Three isoforms/ three dimeric isoenzymes - can be identified through gel electrophoresis
How do you conduct the gel electrophoresis?
on cellulose acetate strips
What are the three isoforms of creatine kinase?
MM, MB and BB
What is the only place in which the MB isoform is found?
Cardiac muscle/ myocardium
How much of total creatine kinase does MB isoform represent in the myocardium?
about 15%, the rest is MM
Which isoform moves closest to the negative electrode?
MM isoform
What is myocardial infarct?
death of heart muscle cells
why do the heart muscle cells die?
lack of oxygen
Why would there be a lack of oxygen in the heart muscles?
Blockage of the cardiac arteries. This process is termed atherosclerosis.
Why do cells need oxygen, how do they use it and why do cells die without it?
ATP is generated Via glycolysis, the Krebs Cycle and eventually oxidative phosphorylation.
The end point of the process requires atmospheric oxygen, hence if there is less oxygen supplied to a cell there is less ATP, pumps do not function, ion balance is lost and cells die.
When and why is creatine kinase found in the blood?
Cell contents are released when they are dying, e.g., proteins that should be held inside against concentration gradients appear in the serum.
Therefore the levels of many proteins including creatine kinase (many others as well such as lactate dehydrogenase) in serum can be used as indirect indicators of cell death
IN what tissues is CK present at high levels?
Creatine kinase is present in all cells at very low levels but is at high concentrations in metabolically very active tissues including the brain, heart and skeletal muscles.
Describe the absorption spectrum for NADH and NAD+?
They are distinct
What technique is used to detect CK activity in the serum?
coupled assay
What is the couples assay for creatine kinase (3 equations)?
creatine phosphate + ADP–> creatine + ATP (via CK)
D-glucose + ATP –> ADP + G6P (via hexokinase)
G6P + NADP+ –> 6-PG + NADPH + H+ (via G6P dehydrogenase)
How then can increased CK be related specifically to the death of cardiac muscle rather than skeletal muscle and brain tissue?
The only tissue where both genes are expressed is cardiac muscle cells. They therefore make all three dimers including the hybrid MB form. (only traces of BB in myocardium)
Thus, death of cardiac muscle fibres can be determined if the MB isoform of CK can be detected in the serum.
Which form of creatine kinase is only expressed in the brain?
BB isoform as the brain only expresses the B gene
Which isoform of creatine kinase is only found in skeletal muscle?
MM form is the only one made in skeletal muscle cells
What is CK?
CK is a protein made from two subunits or monomers i.e., it is a dimer.
The two monomers are coded for by two different genes,
Forming two different monomer isoforms B and M
The two monomers have approximately the same molecular mass but they differ in their pI (isoelectric point)
This means they can separate by charge.
