Chem path 16 - Enzymes and cardiac markers Flashcards
Which type of enzyme is released first from a necrosed cell?
Cytosolic enzymes are released before subcellular enzyme
In which two places can enzymes be measured?
In the serum (injury) and in the tissue (abnormalities)
How can iso-enzymes be separated out?
Electrophoresis (isoenzymes have different Kms)
What is Km (Michaelis-Menten constant)
=[substrate] at which reaction velocity is 50% of the maximum
What do high and low Kms indicate?
High Km = weak binding
Low Km = strong binding
Where is ALP found?
BLIP (bone liver intestines placenta)
When is an elevated ALP physiological?
During pregnancy (third trimester) and childhood
ALP is high in bone diseases associated with which type of activity?
Osteoblastic activity
What is the clinical approach to unexplained ALP/
- LFTs (GGT and ALT)
- Check vitD
- ALP isoenzymes - performed by electrophoresis test
Which 3 ways can bone and liver ALP be differentiates?
GGT measurement
Electrophoresis separation
Bone ALP immunoassay
Pathological causes of raised ALP <5x upper limit
Bone - tumours, fractures, osteomyelitis
Liver - Infiltrative disease, hepatitis
Pathological causes of raised ALP >5x upper limit
Bone - Paget’s disease, osteomalacia
Liver - Cholestasis, cirrhosis
Is ALT or AST more speciifc to the liver?
ALT
What numerical cut off of ALT is highly suggestive of paracetamol OD?
ALT >1000 (ULN 45)
In which conditions does an elevated LDH carry a poor prognosis?
Germ cell testicular cancer or lymphoma
What is amylase a marker of?
Acute pancreatitis
What else is often measured as a marker of acute pancreatitis?
Pancreatic lipase
Which other gland produces an amylase isoenzyme?
Salivary glands - amylase can be raised in parotitis (mumps)
What do you measure in chronic pancreatitis?
Foecal elastase
What is a common SE of statins?
Statin-related myopathy
Which creatine kinase isoenzyme can help make the diagnosis of statin-related myopathy?
CK-MM (>10X UL)
What are the clinical syndromes of statin-related myopathy
Myalgia –> rhabdomyolysis
Name some risk factors for statin-related myopathy
Polypharmacy (other drugs metabolised by CYP3A4 e.g. clarithromycin, fibrates, cyclosporin) High doses genetic predisposition previous myopathy with statins vitamin D deficiency
Other than statins, what are some other causes of raised CK?
MI, Myositis, myopathy e.g. Duchenne’s, severe exercise, physiological (AFC)
