Enzymes: Amylase/Lipase Flashcards
What reaction does alpha amylase catalyze?
Catalyzes the hydrolysis of alpha-1,4-glycosidic bonds in polymers of glucose
What are the 2 types of amylase?
Beta and alpha
What is the cofactor required for amylase catalytic activity?
Calcium
What is the pH optimum for amylase catalytic activity?
6.9-7.0
Is it normal to find amylase in the urine?
Yes, amylase is small enough to be filtered by the glomerulus of the kidney
What are activators for amylase activity?
Univalent anions, such as Chloride or Bromide
Amylase is inhibited by all anticoagulants except:
Heparin
How long is amylase stable at room temperature?
1 week
How long is amylase stable at refrigerated temperature?
2 months
What is endoamylase?
Hydrolysis occurs at random locations in the polysaccharide
What sort of amylase is endoamylase?
Alpha amylase
What is exoamylase?
Enzyme found in plants and bacteria only. It acts only on the bonds at the terminal end of a glucose chain.
What type of amylase is exoamylase?
Beta amylase
If a specimen needs to be diluted for amylase measurement, what do you need to use to dilute it?
Saline
In amylase measurement, why does saline need to be used instead of water?
If water is used, chloride will be diluted considerably. Chloride is needed to activate the reaction catalyzed by amylase.
Where is amylase found?
Found in many tissues throughout the body
Where are the highest amylase concentrations found?
Pancreas and salivary glands
How many salivary isoenzymes are there?
3 - S1, S2, S3
How many pancreatic isoenzymes are there?
3 - P1, P2, P3
Amylase is stable until what temperature is reached?
50 degrees Celsius
How is the pain associated with acute pancreatitis caused?
Proteolytic enzymes are released throughout the pancreas, causing tissue destruction and leading to the epigastric pain. This is called autolysis.
Why does amylase increase so drastically in acute pancreatitis?
The autolysis associated with the proteolytic enzymes causes a release of pancreatic amylase into the serum.
When does serum amylase increase in acute pancreatitis?
5-8 hours after disease onset
When do serum amylase levels peak in acute pancreatitis?
They peak with 24 hours of disease onset
When do serum amylase levels return to normal after an attack of acute pancreatitis?
Return to normal range in 3-5 days
When do urine amylase levels return to normal after an attack of acute pancreatitis?
Will remain elevated for up to 10 days
What disease states is acute pancreatitis associated with?
Alcoholism, hyperlipemia, uremia, hyperparathyroidism, trauma
Is the serum amylase level specific for pancreatitis?
Serum amylase levels can be elevated in a wide variety of disease states
What is macroamylasemia?
Amylase will complex with immunoglobulins, forming a large complex that can not be cleared from the serum by the kidneys
What immunoglobulins will amylase complex with when macroamylasemia is present?
IgG or IgA
In macroamylasemia, will serum amylase be increased, decreased, or normal?
Increased
In macroamylasemia, will urinary amylase be increased, decreased, or normal?
Normal or decreased
How can macroamylasemia and acute pancreatitis be differentiated?
Calculate the amylase clearance/creatinine clearance ratio
What is the formula for the amylase clearance/creatinine clearance ratio?
(Urine amylase x serum creatinine)/(serum amylase/urine creatinine) x 100%
What is the normal ACCR?
2-5%
If the ACCR is less than 2%, what does this indicate?
Macroamylasemia
If the ACCR is increased, what does this indicate?
Acute pancreatitis
What is the modified saccharogenic method?
A polysaccharide is hydrolyzed by amylase to form reducing sugars. The increasing levels of reducing sugars are measured using the hexokinase method.
What must be corrected for in the modified saccharogenic method?
Endogenous glucose, which will falsely increase the results
How do you correct for endogenous glucose in the modified saccharogenic method?
Use a serum blank and subtract glucose from the blank from the result. Or you can allow 10 minutes preincubation to allow glucose in the sample to react.
What type of amylase normally dominates in the serum?
S type
What type of amylase dominates normally in the urine?
P type
How would you further differentiate amylase isoenzymes?
Use isoenzyme fractionation
What methods can be used for amylase isoenzyme fractionation?
Electrophoresis, isoelectric focusing, chemical inhibition, inhibition of salivary amylase with monoclonal antibodies
During isoenzyme fractionation, amylase enzymes of which origin will migrate the fastest?
Salivary origin
What are the most commonly observed amylase isoenzyme fractions?
P2, S1, S2
In acute pancreatitis, what amylase isoenzyme is predominant?
P3
What reaction does lipase catalyze?
Lipase catalyzes the hydrolysis of dietary triglycerides with long chain fatty acids.
What is required by lipase for optimal activity?
Colipase, protein secreted by the pancreas
