[LAB] AST/ALT Flashcards
→ Biologic proteins that catalyze chemical reactions without being consumed.
enzymes
→ They speed up reactions without altering equilibrium or being changed.
enzymes
What are the six major classes of enzymes?
→ Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases.
What type of enzyme is aspartate aminotransferase (AST)?
Transferase
What type of enzyme is lactate dehydrogenase (LD)?
Oxidoreductase
→ It transfers functional groups between molecules.
transferase
Where are enzymes commonly found in the body?
→ In all body tissues and frequently in serum after cellular injury.
→ The substance that an enzyme acts upon.
substrate
→ The region where the substrate binds and the reaction occurs.
active site
→ A site other than the active site where regulatory molecules bind.
allosteric site
What is the International Unit (IU) of enzyme activity?
→ The amount of enzyme that catalyzes 1 µmol of substrate per minute.
What is the SI unit for enzyme activity?
→ Katal (mol/s).
What is the standard unit for enzyme concentration in the lab?
→ IU/L or kat/L.
What is the conversion factor between IU and nkat?
→ 1.0 IU = 17 nkat.
What reaction order is enzyme activity measured at in the lab?
→ Zero-order kinetics.
What are some conditions that must be controlled in enzyme assays?
→ pH, temperature, and absence of inhibitors.
What are the two main types of enzyme measurement methods?
→ Kinetic and endpoint methods.
What does an increase in enzyme absorbance indicate in a kinetic assay?
→ Increased enzyme activity.
What reaction does AST catalyze?
→ The transfer of an amino group between aspartate and α-ketoglutarate.
What coenzyme is required for AST activity?
→ Pyridoxal phosphate.
What are the major tissue sources of AST?
→ Liver, cardiac tissue, skeletal muscle, kidney, pancreas, erythrocytes.
What are the two AST isoenzymes?
→ Cytoplasmic AST and Mitochondrial AST.
What laboratory method is commonly used to measure AST?
→ The Karmen method.
It is a coupled enzymatic reaction that measures absorbance change at 340 nm.
Karmen method
What wavelength is used to measure AST in the Karmen method?
→ 340 nm.
What reagent is used in the Reitman-Frankel AST method?
→ 2,4-Dinitrophenylhydrazine (DNPH).
What is the color change in the Reitman-Frankel AST method?
→ Intense brown.
What is the normal reference range for AST levels?
→ 6-37 U/L (37°C).
What is another name for ALT?
→ Serum glutamate-pyruvate transaminase (SGPT).
What reaction does ALT catalyze?
→ The transfer of an amino group from alanine to α-ketoglutarate.
What coenzyme is required for ALT function?
→ Pyridoxal phosphate.
What are the primary tissue sources of ALT?
→ Liver and cardiac tissue.
What laboratory method is commonly used to measure ALT?
→ The Karmen method.
What is the indicator enzyme in the Karmen method for ALT?
→ Lactate dehydrogenase (LD).
What reagent is used in the Reitman-Frankel ALT method?
→ 2,4-Dinitrophenylhydrazine (DNPH).
What is the final product detected in the Reitman-Frankel ALT method?
→ Ketoacid hydrazone.
What is the reference range for ALT levels?
→ 6-37 U/L (37°C).
What laboratory factors can falsely elevate ALT levels?
→ Bilirubin, erythromycin, iproniazid, morphine, endogenous pyruvate.
What factors can falsely decrease ALT levels?
→ Presence of heavy metals like mercurial diuretics.
all enzymes we measure are found in the ____
serum
AST Substrate:
ALT Substrate:
L-aspartate
L-alanine
Indicator enzyme in AST
Malate dehydrogenase
When NADH is oxidized to NAD+ in the karmen method, the absorbance is (increased/decreased)
Decreased
Optimal pH for AST/LT method
7.0 - 8.0
AST are found to be decreased in the _________
urethra
kaya decreased in uremia
Most common AST isoenzyme
Cell cytoplasm AST
If you have necrosis, what AST isozenzyme increases?
Mitochondrial AST
pH must be at least close to the _______’s pH
Body’s pH (7.4)
Non-CHON molecule of enzymes necessary for enzyme activity
Co-factors
Activator (INORGANIC) / Co-enzymes (ORGANIC):
Chloride, bromide, magnesium, iron, zinc, copper, calcium, manganesem cobalt, potassium
Activator/Organic
2.6.1.1
What is 2?
Class
2.6.1.1
What is 6?
Sub group
2.6.1.1
What is the first 1?
sub-sub group
2.6.1.1
What is the second 1?
serial number
2.6.1.1
What is this enzyme?
Aspartate aminotransferase (AST)
breakage of bonds with hydrolysis
Hydrolases
breakage of bonds without hydrolysis
Lyases
classification of the enzyme where there conversion of geometric or position of isomers
Isomerases
Class no: Oxidoreductases
1
Class no: Transferases
2
Class no: Hydrolases
3
Class no: Lyases
4
Class no: Isomerases
5
Class no: Ligase
6
