session 3-enzyme activity,zymogens and clot breakdown Flashcards
What is Km?
substrate concentration that gives 1/2 Vmax
What is Vmax?
maximum rate of reaction when enzyme is saturated with substrate
What happens to Vmax and Km during non competitive inhibition?
- Vmax=not reached because active site shape is changed and so max velocity cannot be reached
- Km=unaffected
What happens to Vmax and km in competitive inhibition?
- Km=increased due to blocking of active site and therefore a higher velocity is reached before enzyme is saturated with substrate (adding substrate will overcome effect of inhibitor)
- Vmax=unaffected
what is allosteric control?
Binding of an activator/inhibitor at a place other than the active site of protein to regulate it and could change how enzyme functions
What is positive/negative cooperativity when referring to allosteric effectors?
-inhibit or activate an enzyme
what type of enzymes add and remove phosphate groups to proteins?
- add=kinase
- remove=phosphatase
what is a zymogen?
-inactive precursor of an enzyme which is converted into an enzyme when activated by another enzyme
what activates PFK in glycolysis?
AMP and fructose-2,6-bisphosphate
what is the Michaelis-Menten equation?
Vo= Vmax [s]/Km + [s]
what inhibits PFK in glycolysis?
ATP,citrate and H+
how do phosphate groups affect enzymes?
- bulky and charged
- affect enzyme conformation and substrate binding
Zymogens are inactive precursors of enzymes. Name an enzyme and zymogen located in the stomach
zymogen=pepsinogen
enzyme=pepsin
give 2 examples of a zymogen and its enzyme in the pancreas
Zymogen=proelastase
Enzyme=elastase
Zymogen=chymotrypsinogen
Enzyme=chymotrypsin
what does the concentration of zymogens do in terms of clot formation and breakdown?
- dilute clotting factors by blood flow
- removed by liver
How do proteases breakdown clot?
-Digested e.g. 8a degraded by protein C
What does AT3 (antithrombin 3) do?
-Breaks down thrombin with the help of HEPARIN
what does fibrinolysis mean?
breaking down of clot
what does T-PA stand for and what does it do?
tissue plasminogen activator-breaks down blood clots by turning plasminogen into plasmin which in turn causes fibrin to turn into fragments. (with the help of STREPTOKINASE)
Activation of Zymogens in the pancreas are controlled by what enzyme?
Trypsin
Describe in 3 steps how emphysema is caused-(clue:deficiency in protein enzyme inhibitor)
- deficiency in alpha-anti trypsin protein inhibitor
- needed to stop trypsin activity (which activates other enzymes including elastase)
- therefore continuous activation of elastase occurs=destroys alveolus walls
What do the Kringle domains do on prothrombin?
Keeps thrombin in inactive form
What is the role of gal domains?
Localise clot to site of damage
Which enzyme, when activated from the pro…. Version of itself by thrombin, catalyses cross linking between fibrin to form clot?
Transglutaminase
What three ways can an enzyme be changed?
- allosteric regulation
- covalent modification
- proteolytic cleavage
Give an example of an enzyme that is allosterically controlled. Hint:glycolysis
PFK
Give an example of covalent modification.
Phosphorylation (addition of phosphate=kinase, removal=phosphatase)
Give 3 examples of proteolytic cleavage enzyme activation.
- insulin (preproinsulin)
- digestive enzyme
- blood clotting
- apoptosis
What is an isoenzyme?
Each of two or more enzymes which same function but different structure
