Enzyme Regulation Flashcards
The cell needs to be able to regulate:
- when a reaction occurs
- how much product is produced from a reaction
Why does enzyme activity need to be regulated?
so that they function at the proper time and place
Name 5 ways enzyme activity is regulated
- controlling the amt of enzyme present
- allosteric regulation
- feedback regulation
- produce enzyme in an inactive form (zymogen or proenzyme)
- covalent modification
What determines enzyme quantity?
rate of synthesis and breakdown of enzyme
The quantity of an enzyme may be :
- increased by raising its rate of synthesis
- or decreased by lowering its rate of synthesis
An allosteric enzymes has another
binding site
Effector molecules change the activity of an
allosteric enzyme by binding to the other site
Some effectors
- speed up enzyme action (positive effectors)
- slow down enzyme action (negative effectors)
Allosteric effectors can be
products, substrate, and so on
If too much product is created the enzyme may be shut off by an
intermediate becoming an allosteric inhibitor
Feedback inhibition is a
common form of enzyme regulation in which the product inhibits the enzyme
A zymogen is
an enzyme produced in an inactive form
Zymogens (proenzymes) are converted to their active form when
needed by removing a part of the zymogen
Wha’ts an example of zymogens?
the digestive enzymes
Covalent modification
adding/removing groups-like phosphate groups
Phosphate groups are located at the OH of
serine
threonine
tyrosine
Isozymes
enzymes catalyzing the same biochemical reaction
Isozymes have
different chemical composition and are found in different tisues
e.g. LDH lactate dehydrogense and CK creatine kinase
2 different polypeptide chains (M and B) combine to give 3 isozymes:
CK-MM (muscle)
CK-MB (heart)
CK-BB (brain)
Enzymes are released from
injured tissue into blood
If CK-MB is found in the blood stream,
this suggest myocardial infarction
Some isozymes in blood are indicative of
tissue damage, used for clinical diagnosis
Increase in serum levels of H4 relative to H3M are
indicative of myocardial infarction (heart attack)
