(Transcribed from Dr. Laville’s lecture, 23 Feb 2000 by Brian Buschman)
Return to Semester One Goodies
Return to The Unofficial Ross Page
Enzymes exist in the body to catalyze various biochemical reactions. It is difficult and expensive to directly measure a bodily enzyme then it is to measure it’s effect in the change of either substrate or product concentrations. Most enzymes are present primarily in cells and not in plasma. This property makes them a useful tool for diagnosis as they will be spilled into the plasma when the tissue containing them is damaged. They do all have a base level in the plasma which is related to the rate of release from the given cells and on the renal clearance.
Some enzymes exist in more then one form, isoenzymes, with different isoenzymes present in different tissues even though they all play a similar function. This can be seen in the three isoenzymes of creatine kinase (it’s purpose is to rapidly add Pi back onto ADP in times when the cell needs a quick supply of ATP):
1) CK-MM is found in skeletal muscle.
2) CK-MB is found in cardiac muscle.
3) CK-BB is found in the brain.
Cholinesterase is found in two tissues:
1) Liver
2) Erythrocytes
Due to it’s location you can have elevated cholinesterase levels when either liver the liver is damaged or with renal disease (nephrotic syndrome).
Transaminases can be found in two forms:
1) Aspartate transaminases (AST), which is found in cardiac, skeletal muscle and liver.
2) Alanine transaminases (ALT), which is found in the heart and liver.
Lactate dehydrogenase (LD) is found in five different isoenzymes in the body:
1) LD1, which is elevated with MI and renal disease.
2) LD2, which is elevated with MI, renal disease, leukemia and malignant tissues.
3) LD3, which is elevated with leukemia and malignant tissues.
4) LD4 and LD5 are elevated with damage to the liver or skeletal muscle.
GGT is raised with liver disease/damage or by many drugs.
Elevated with bone disease
Found in prostate, liver and some blood cells but elevated levels are usually due to prostate problems.
Is a digestive enzyme and will be elevated in the blood with intestinal obstructions or ruptured ectopic pregnancy.
After a MI there are three enzymes that will rise and fall according to a regular time schedule and may be used in the ER to determine how long ago the MI occurred.
|
Enzyme |
Starts to rise (hrs) |
Peaks (days) |
Back to normal (days) |
|
CK |
4-6 |
1-2 |
3-5 |
|
AST |
6-8 |
1-2 |
4-6 |
|
LD1,2 |
12-24 |
2-3 |
7-12 |
This a summary from the last page of her handout and I believe is all that we will have to memorize for the sake of this course but that is something for you to decide for yourself.
|
Condition |
Enzymes Elevated |
|
MI |
CK-MB, LD1,2, AST |
|
Liver Disease |
ALT, AST, GGT |
|
Bone Disease |
ALP |
|
Prostate Cancer |
ACP |
|
Acute Pancreatitis |
a-amylase |
|
Muscle tissue damage |
CK-MM |
Return to Semester One Goodies
Return to The Unofficial Ross Page