What is the function of Amylase?

Splits alpha 1,4 linkages in glycogen and starch

(Glycogenolysis)

What are the tissue sources of Amylase?

• Pancreatic Cells (P-type isoenzyme)
• Salivary Glands (S-type isoenzyme)
• Lesser amounts in:
• Skeletal muscle, small intestine, and fallopian tubes 

1. Saliva
2. Plasma
3. Urine

What are the 2 most popular analytical methods of Amylase measurement?

-Amyloclastic

-Continuous Monitoring 

Measures the disappearance of starch by monitoring the changes in iodine-starch binding 

Dark brown--->yellow

*Most popular method 

Coupled enzyme system measures amount of NADH formed.

Measure at 340nm

• Serum or urine with pH adjusted to 7.0
• Heparinized plasma only
• Hemolysis may interfere depending on the method

What are some interfereing substances of Amylase measurement?

• Morphine/opiate derivatives
• constrict pancreatic ducts=false increase in amylase levels
• Triglycerides 
• elevations may mask some elevation of amylase

• Pancreatic Disease: 
• Pancreatitis, Pancreatic Trauma, Pancreatic Carcinoma
• Non-Pancreatic Disease:
• Salivary gland, Tumors, Diabetic Ketoacidosis, Biliary Tract Disease

• Begin to rise: 2-12 hours
• Peak: 24 hrs
• Return to normal: 3-5 days

What is Macroamylasemia?

In Pacreatitis: Increase ratio in urine 

In Macroamylasemia: Decrease ratio in urine

What is the function of Lipase?

• Pancreas (Primary site!!)
• Tongue
• Gastric secreations/intestine
• Lungs
• WBC 
• Adipose tissue

1. Titrimetric
2. Turbidometric
3. Colormetric/Continuous monitoring 

Triglyceride substrate (olive oil, triolein) emulsified by lipase in the sample

(Time consuming and considered the reference method)

Reduction of the turbid appearence of a triglyceride substrate in water is measured as lipase breaks it down.

*Triolein commonly used

(difficult to compare assays when different substrates are used in the method)

What is the Colormetric/Continuous Monitoring method in lipase measurement

What are the sample requirements for Lipase?

• Serum/Plasma, ascities/pleural fluid
• Heparin should be avoided due to false increase
• Hemolysis (Hemoglobin) can inhibit lipase activity causing falsely low results

• Acute Pancreatitis: 
• Mimics amylase levels, but more specific and less sensitive
• not cleared in the kidneys so remains elevated for a longer time (8-14 days)
• Other intra-absominal disorders
• Inflammatory or obstuctive disorders, acute or chronic renal disease

What is the cause of decreased Lipase levels?

What is the function of Gamma-Glutmyl Transferase (GGT)?

Membrane bound enzyme that plays a role in:

1.Glutathione metabolism

2.Reabsorption of amino acids from the glomerular filtrate and intestinal lumen

• Liver**
• Kidney
• Pancreas
• Prostate

GGT found in the serum comes from..

What is the analytical method used to measure GGT

• Use glycine as acceptor of glutamyl residue from substrate and p-nitroanaline is released
   
• Level of p-nitroanaline can be colormetrically measured at 410nm

What are the sample requirements for GGT?

• Serum or plasma (heparin)
• (Citrate, oxalate, and fluroide can depress activity)
• Sample must be free of hemolysis due to colormetric reaction

• GGT is most specific but least sensitive of the liver function tests (may take a while for levels to rise)
   
• Increases seen in:
• Chronic ingestion of alcohol or certain drugs*
• liver disease 
• pancreatic disease 

What is the function of Cholinesterases

• "True" Cholinesterases (cholinesterase I)
• acts as a neurotransmitter
• Pseudocholinesterase (cholinesterase II)
• Tested clinically 

• Plasma
• Liver
• Pancreas
• White matter

Photometric 

1. Add thiocholine containing substances
2. Breakdown of choline containing substances realeases free thiocholine
3. Thiocholine combines with colored chromagen

What are the sample requirements for cholinesterase?

• Serum or plasma
• Prefer citrate or fluoride anticoagulants 
• Free from hemolysis (its found in RBC, false Inc)
• Repeated freezing and thawing can cause a 30% decrease in cholinesterase activity

Decreased Levels!!!

• Leads to inability to efficiently breakdown many choline containing compounds

• Organophosphate insecticide poisoning (inhibits enzyme)
• Loss of livers synthetic capacity due to disease
• Gene mutation