Ch. 13 - Enzymes (GGT - G6PD) (RVSP) Flashcards
Serves as the gamma-glutamyl donor in most biologic systems
Glutathione
Enzyme involved in the transfer of gamma-glutamyl residue from gamma-glutamyl peptides to amino acids, H2O, and other small peptides
Gamma-glutamyltransferase (GGT)
3 functions of GGT
- synthesis of peptides and proteins
- regulation of tissue glutathione levels
- transport of amino acids across cell membranes
Tissue sources of GGT
Kidney Brain Prostate Pancreas Liver
Enzyme used for evaluation of liver and biliary system disorders
GGT
Enzyme elevated in all hepatobiliary disorders
GGT
Enzyme increased in patients receiving enzyme-inducing drugs
GGT
Elevated enzyme in chronic alcoholism
GGT
Substrate for GGT analysis
Gamma-glutamyl-p-nitroanilide
Absorbance range in GGT analysis
405-420 nm
Length of time and temperature that GGT activity is stable
1 week at 4°C
Reference ranges for GGT
M: 6-55 U/L (37°C) (0.1 - 0.9 ukat/L)
F: 5-38 U/L (37°C) (0.1 - 0.6 ukat/L)
Class of amylase
Hydrolase
Enzyme that catalyzes the breakdown of starch and glycogen
Amylase (AMY)
Enzyme that attacks only alpha, 1-4 glycosidic bonds
Alpha-AMY
Degradation products produced after alpha-AMY attacks the alpha, 1-4 glycosidic bonds
- glucose
- maltose
- dextrins
Intermediate chains consisting of alpha, 1-6 branching linkages
Dextrins
2 components of starch
Amylose
Amylopectin
Component of starch; long, unbranched chain of glucose molcules, linked by alpha, 1-4 glycosidic bonds
Amylose
Component of starch; branched-chain polysaccharide with alpha, 1-6 glycosidic linkages at the branch points
Amylopectin
Important enzyme in the physiologic digestion of starches
AMY
2 ions needed by AMY for its activation
Calcium ion (Ca2+) Chloride ion (Cl-)
2 major tissue sources of AMY
Acinar cells of the pancreas
Salivary glands
Minor tissue sources of AMY
Skeletal muscle
Small intestine
Fallopian tubes
Urine
Smallest enzyme
AMY
Where digestion of starches start
Mouth
Enzyme in the mouth that hydrolyzes starches
Salivary AMY
Performs the major digestive action of starches once the polysaccharides reach the intestine
Pancreatic AMY
Inactivates salivary AMY
Acidity of gastric contents
Diagnostic significance of serum and urine AMY
Acute pancreatitis Salivary gland lesions Intraabdominal diseases Renal insufficiency Diabetic ketoacidosis Hyperamylasemia
Time when AMY levels begin to rise in acute pancreatitis
5-8 hours after onset of attack
Time when AMY levels are at peak in acute pancreatitis
24 hours
Time when AMY levels return to normal in acute pancreatitis
3-5 days
Condition when the AMY molecule combines with immunoglobulins to form a complex that is too large to be filtered by the glomerulus
Macroamylasemia
AMY isoenzyme derived from pancreatic tissue
P-type
AMY isoenzyme derived from salivary gland tissue, fallopian tube and lung
S-type
AMY isoenzymes that migrate the fastest in electrophoresis
S-type (S1, S2 and S3)
AMY isoenzymes that migrate slowly in electrophoresis
P-type (P1, P2 and P3)
Most commonly observed AMY isoenzyme fraction in electrophoresis
P2
S1
S2
Predominant AMY isoenzyme in acute pancreatitis and renal failure
P3
4 methods for AMY assay
- Amyloclastic/Iodometric method
- Saccharogenic method
- Chromolytic/Chromogenic Labelled Substrate method/Colorimetric
- Couple Enzyme Reaction/Continuous-monitoring technique
AMY method; measures the disappearance of starch substrate
Amyloclastic
AMY method; measures the appearance of the product (reducing sugars)
Saccharogenic
AMY method; measures the increasing color from production of product coupled with a chromogenic dye
Chromogenic/Chromolytic/Colorimetric
AMY method; coupling of several enzyme systems to monitor amylase activity
Continuous monitoring/Coupled Enzyme reaction