Podcast
Questions and Answers
In which conditions are the highest levels of aspartate aminotransferase (AST) observed?
In which conditions are the highest levels of aspartate aminotransferase (AST) observed?
- Cirrhosis (correct)
- Acute myocardial infarction
- Skeletal muscle injury
- Viral hepatitis (correct)
What is the primary tissue source for high concentrations of AST?
What is the primary tissue source for high concentrations of AST?
- Skeletal muscle
- Kidney
- Erythrocytes
- Cardiac tissue (correct)
What would be a significant source of error in AST testing?
What would be a significant source of error in AST testing?
- Using a freshly drawn serum sample
- Conducting the assay with the appropriate controls
- Delayed transport of the serum sample (correct)
- Storing the serum at room temperature (correct)
Which of the following statements about serum stability of AST is true?
Which of the following statements about serum stability of AST is true?
What is an expected AST level increase in cases of skeletal muscle involvement?
What is an expected AST level increase in cases of skeletal muscle involvement?
What is the primary role of aspartate aminotransferase (AST) in metabolic processes?
What is the primary role of aspartate aminotransferase (AST) in metabolic processes?
Which coenzyme is required for the enzymatic activity of aspartate aminotransferase?
Which coenzyme is required for the enzymatic activity of aspartate aminotransferase?
What could be a common source of error in the testing of AST levels?
What could be a common source of error in the testing of AST levels?
Which is true regarding the isoenzymes of aspartate aminotransferase?
Which is true regarding the isoenzymes of aspartate aminotransferase?
What is the typical reference value range for serum AST levels in adults?
What is the typical reference value range for serum AST levels in adults?
In the clinical analysis of AST, which condition might be indicated by elevated AST levels?
In the clinical analysis of AST, which condition might be indicated by elevated AST levels?
What is one critical factor in ensuring serum stability and storage for AST testing?
What is one critical factor in ensuring serum stability and storage for AST testing?
Which method is commonly used to determine the enzymatic activity of AST?
Which method is commonly used to determine the enzymatic activity of AST?
Which isoenzyme of Aspartate Aminotransferase (AST) is predominantly found in serum?
Which isoenzyme of Aspartate Aminotransferase (AST) is predominantly found in serum?
What is the significance of increased levels of the mitochondrial isoenzyme of AST?
What is the significance of increased levels of the mitochondrial isoenzyme of AST?
What enzyme activity assessment method is the basis for measuring AST activity?
What enzyme activity assessment method is the basis for measuring AST activity?
What is the optimal pH range for the enzyme activity assay of AST?
What is the optimal pH range for the enzyme activity assay of AST?
What reference range is established for AST activity at 37°C?
What reference range is established for AST activity at 37°C?
Which substance is used as an indicator in the AST enzyme activity assay?
Which substance is used as an indicator in the AST enzyme activity assay?
What is one reason why isoenzyme analysis of AST is not routinely performed?
What is one reason why isoenzyme analysis of AST is not routinely performed?
What can cause errors in AST testing results?
What can cause errors in AST testing results?
Study Notes
Isoenzymes of Aspartate Aminotransferase (AST)
- Two isoenzymes: Cytoplasmic (predominant in serum) and Mitochondrial (increased in cellular necrosis).
- Intracellular AST concentration is 7,000 times higher than extracellular levels.
- Isoenzyme analysis is not routinely performed in clinical settings.
Assay for AST Enzyme Activity
- Based on Karmen Method utilizing a coupled enzymatic reaction.
- Monitored using Malate Dehydrogenase, tracking absorbance changes at 340 nm.
- Measures the oxidation of NADH to NAD+.
- Optimal pH range is between 7.3 to 7.8.
- Reference range for AST activity is 5 to 35 U/L (37°C), equivalent to 0.1 to 0.6 µkat/L.
Nomenclature and Function of AST
- Enzyme Classification: E.C. 2.6.1.1.
- Formerly known as Serum Glutamic Oxaloacetic Transaminase (SGOT).
- Catalyzes transfer of an amino group between aspartate and α-keto acids.
- Coenzyme required for activity: Pyridoxal phosphate (Vitamin B6).
Tissue Sources of AST
- High concentrations found in cardiac tissue, liver, and skeletal muscle.
- Lower concentrations noted in kidneys, pancreas, and erythrocytes.
Diagnostic Significance of AST
- Markedly elevated in acute hepatocellular disorders, with viral hepatitis levels reaching up to 100 times the upper limit of normal (ULN).
- Cirrhosis levels are approximately 4 times ULN.
- In skeletal muscle involvement, AST levels may increase 4-8 times ULN.
- Can indicate acute myocardial infarction (AMI).
Clinical Relevance of Aminotransferases
- Used to evaluate liver function and muscle damage.
- Results correlate with both physiologic and pathologic conditions, aiding in diagnosis and management of diseases.
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Description
This quiz covers the study of Aspartate Aminotransferase (AST) isoenzymes, focusing on their characteristics and clinical significance. It includes details about cytoplasmic and mitochondrial isoenzymes, as well as their concentration differences. Test your knowledge on how these isoenzymes are analyzed in clinical settings.
