TUT 4 Flashcards
(16 cards)
What is a “U” (or Unit) of an enzyme equivalent to?
Defined as the amount of the enzyme that catalyses the conversion of one micromole of substrate per minute
More enzyme = more substrate = more product
List some biomarkers (enzymes and other in vivo molecules) that are of cardiac origin. Which of these may also be from organs other than the heart?
Troponin 1, LDH 1, creatine kinase, CK-MB, myoglobin
What is a liver function test
Test the levels of a number of proteins and enzymes that are either produced by the liver cells or released into the blood when liver cells are damaged.
List some of the more common laboratory techniques used to assay the different liver and cardiac markers?
Electrophoresis, spectrophotometry, immunoassays, high power liquid chromatography
What is an isozyme (isoenzyme)? How are these separated from each other for individual analysis?
Enzymes that differ in amino acid sequence that make them favour forwards or reverse reaction but catalyze the same reaction. Different Km and Vmax like hexokinase and glucokinase.
>Separated by electrophoresis
How many isozymes are known for a. Lactate Dehydrogenase? b. Creatine Kinase (or Creatine Phosphokinase)?
- LDH 1 (heart + RBC), LDH 2 (WBC), LDH 3 (lungs), LDH 4(kidneys, placenta, pacncreas), LDH 5 (liver and skeletal muscle)
- CK-MM (skeletal), CK-MB (cardiac), CK-BB (brain). Made up of two peoly peptides with slightly different aa
What is the significance of the different isozymes (eg Lactate Dehydrogenase and Creatine Kinase)?
Biomarkers that can be measured –> appearance of different isoenzymes like LDH1 or LDH5 in the blood test tells us about the origin of the problem (heart or liver)
What is the physiological role of myoglobin?
Carrying oxygen to muscle tissues through its heme group ( 1 polypeptide chain)
Why may elevated myoglobin be one of the first markers of a Myocardial Infarction (MI)?
Small molecular weight and high sensitivity, so its released more rapidly from MI than troponin and CK-MB. Elevated levels can be measured a few hours following MI.
What is the physiological role of troponin?
Group of proteins found in skeletal msucle and heart muscle fibres that regulate muscular contraction.
>Calcium ion regulator
Why is troponin I (or T) a useful marker of a MI?
Most specific marker of MI, found most in sacromere of cardiac myocytes
What is C-reactive protein?
Blood test marker for inflammation in the body, it is produced in the liver.
Which hepatic markers are specific for hepatic disease?
- Alanine Transaminase
- Aspartate Transaminase
- Alkaline Phosphatase
- Gamma-Glutamyl Transpeptidase
- Bilirubin
- Albumin
In what form(s) does bilirubin appear in the blood? How might this appear in liver disease?
- Unconjugated but albumin bound
- In liver disease, conjugated billurubin levels elevate
Unconjugated (Unbound to something covalently but will bind to fats)
Conjugated (adding glucoronic acids to make it more water soluble and less toxic –> occurs in the liver), covalently bound
Which biomarkers would you measure in a suspected heart attack?
Troponin I/T, LDH 1, creatine kinase, CK-MB, myoglobin
Which biomarkers would you measure in a suspected liver disease
Alanine Transaminase (ALT) with Aspartate transaminase (AST), bilirubin(unconjugated and total), LDH
Hepatic disease (high levels of ALT and ALP)
Post hepatic (ALP levels high, ALT(hepaitc marker is normal))
Pre-hepatic (High billirubin, ALT is nromal and ALP is normal) –>haemolysis and anaemia
