AMINOTRANSFERASES Flashcards
ASPARTATE AMINOTRANSFERASE (AST)
EC
E.C. 2.6.1.1
AST
Current name
Levo-Aspartate 2-Oxaloglutarate
Aminotransferase
AST
Former name
Formerly:
Serum Glutamic Oxaloacetic Transaminase (SGOT)
Physiologic function of AST
Involved in the transfer of an amino group between aspartate and a-keto acids.
AST
Coenzyme:
Pyridoxal phosphate
Activated - Vitamin B6
Tissue sources of AST
High Concentrations:
Cardiac Tissue
Liver
Skeletal Muscle
Tissue Sources of AST
Lower Concentrations:
Pancreas
Erythrocytes
Kidney
Diagnostic significance of AST
Acute Hepatocellular Disorders
Skeletal Muscle Involvement
Acute Myocardial Infarction (AMI)
Disorder in AST
• Highest levels observed
Acute Hepatocellular Disorders
AST in
• In viral hepatitis:
up to 100 times Upper Limit Normal
AST in
• In cirrhosis:
approximately 4 times Upper Limit Normal
AST
• Levels increase (4-8× ULN)
Skeletal Muscle Involvement
MARKER OF ACUTE MYOCARDIAL INFARCTION
AST
Starts
Peaks
Normal
Starts - 6-8hrs
Peaks - 18-24hrs
Normal - 4-5days
AST Isoenzymes?
• Cytoplasmic Isoenzyme
• Mitochondrial Isoenzyme
• Cytoplasmic Isoenzyme
• Mitochondrial Isoenzyme
AST Isoenzymes
predominant in serum
Cytoplasmic Isoenzyme
AST isoenzyme
increased in cellular necrosis
Mitochondrial Isoenzyme
AST Isoenzymes
Concentration:
Intracellular AST:
7,000 times higher than extracellular
AST Isoenzymes
Clinical Analysis:
Isoenzyme analysis not routinely performed
ASSAY FOR ENZYME ACTIVITY
ASPARTATE AMINOTRANSFERASE (AST)
Principle:
Based on ________
Uses a________
Karmen Method
coupled enzymatic reaction
ASSAY FOR AST
• Indicator: ______________
• Monitors absorbance change at:_____
• Measures_______ to ______
Malate Dehydrogenase
340 nm
NADH oxidation to NAD+
AST
Optimal pH Range:
7.3 to 7.8
AST
Reference range:
5 to 35 Unit/Liter (37°C) (0.1 to 0.6 ukat/L)
SOURCE OF ERROR
ASPARTATE AMINOTRANSFERASE (AST)
Can dramatically increase serum AST concentration
Should be avoided to ensure accurate results
Hemolysis
SOURCE OF ERROR
ASPARTATE AMINOTRANSFERASE (AST)
Stability:
• Stable in serum for…
3 to 4 days
Optimal at refrigerated temperatures
ALANINE AMINOTRANSFERASE (ALT)
EC
E.C. 2.6.1.2
ALT
Present name
Levo-Alanine 2-Oxaloglutarate Aminotransterase
ALT
Formerly:
Serum Glutamic Pyruvic Transaminase (SGPT)
ALT
Physiologic function
Catalyzes the transfer of an amino group from alanine to a-ketoglutarate
ALT
Produces…
glutamate and pyruvate
ALT
Coenzyme:
Pyridoxal phosphate
(Activated Vitamin B6)
ALT is distributed in many tissues, with comparatively high concentrations in the______.
liver
ALT is more ______ specific than AST
Liver
ALT Primary Use:
Evaluation of hepatic disorders
ALT Primary Use:
Higher elevations in_______
Lower elevations in_______
hepatocellular disorders
extrahepatic Or intrahepatic obstructive disorders
ALT
Acute Liver Inflammation:
ALT elevations often higher than_____
ALT remains elevated longer due______
AST
longer half-life (16-24 hours vs. AST)
ALT comparison with AST:
Helps determine the source of elevated AST
Detects concurrent liver involvement with myocardial injury
DIAGNOSTIC SIGNIFICANCE
ALANINE AMINOTRANSFERASE (ALT)
Alcohol-Induced Liver Injury:
Elevated AST/ALT ratio
(De Ritis ratio) of 3 to 4:1
_______ has a longer halflife
Mitochondrial AST
Chronic Liver Conditions:
In cirrhosis,_____ often higher than____ as fibrosis progresses
In end-stage cirrhosis, enzyme levels may be____
AST; ALT
low
AST:ALT ratio
Carcinoma, ALD, Cirrhosis of the liver = >2
Hepatitis = <1
ASSAY FOR ENZYME ACTIVITY
ALANINE AMINOTRANSFERASE (ALT)
Coupled Enzymatic Reaction:
Utilizes Lactate Dehydrogenase (LD) as the indicator enzyme
ALT coupled enzymatic reaction
LD catalyzes reduction of____ to _____
Simultaneous oxidation of ____ to ____
pyruvate to lactate
NADH to NAD+
ALT
Measurement:
• Change in absorbance at______
•______________ to ALT activity
340 nm
Directly proportional
ALT
Optimal pH:
7.3 to 7.8
ALT
Reference range:
7 to 45 U/L (37°C) (0.1 to 0.8 pkat/L)
ASSAY FOR ENZYME ACTIVITY
ALANINE AMINOTRANSFERASE (ALT)
• Colorimetric/Endpoint
• Reitman & Frankel
ALANINE AMINOTRANSFERASE (ALT)
• Reitman & Frankel
• Color developer:
2,4 Dinitrophenylhydrazine (DNPH)
ALANINE AMINOTRANSFERASE (ALT)
• Reitman & Frankel
• Colorimetric/Endpoint
• Color intensifier:
0.4N Sodium hydroxide (NaOH)
Major Organ Affected
AST
ALT
Heart
Liver
Hemolysis
AST
ALT
Affected
Relatively afftected
Reitman & Frankel
Substrate
AST
ALT
Aspartate a-ketoglutarate
Alanine a-ketoglutarate
End products
ALT
AST
Oxaloacetate Glutamate
Pyruvate Glutamate
Coenzyme
AST
ALT
Pyridoxal phosphate (B6)
Color developer
AST
ALT
2,4 Dinitrophenylhydrazine (DNPH)
Color intensifier
AST
ALT
0.4N Sodium hydroxide (NaOH)
