Lecure 14- regulation of protein function Flashcards
What can be noted about enzymes in protein formation?
Changing enzyme activity in pathway changes how the pathway works
What are isoenzymes?
Different forms of the same enzyme that have different properties
What is a co-enzyme?
Non-protein compound necessary for the functioning of an enzyme
What is interesting about allosterically regulated enzymes?
Show a sigmoidal relationship because of two different conformations (t and r state)
How can allosteric inhibitor affect enzyme?
Can lower Vmax as it is a non competitive inhibitor
Give an example of an allosterically regulated enzyme?
Phosphofructokinase. Inhibited by ATP, citrateand H+. More of enzyme in T state. Activated by AMP and fructose 2-6 bisphosphate
What enzymes add phosphate and what enzymes remove phosphate?
Protein kinase adds phosphate and protein phosphates removes phosphate
What’s good about phosphorylation (covalent modification)
Adds to negative charges
Can make H bonds
Rate of phosphorylation/dephosphorylation can be adjusted
Links energy status of cell to metabolism through ATP
Allows for amplification effects
What is an enzyme cascade?
Enzyme amplification process
Interesting about glycogen mobilisation?
Synthesis and breakdown are reciprocally regulated
What is a zygotes?
Inactive substance converted into an enzyme when proteolytic ally cleaved by an enzyme
Give an example of an enzyme activated by proteolytic cleavage?
Digestive enzymes synthesised as zymogens eg pepsinogen to pepsin.
Chymotrypsinogen to chymotrypsin
How do we control enzymes?
Degradation
Irreversibly bind inhibitor
Alpha 1 antitrypsin deficiency?
Inhibits a range of proteases one of which is elastase.
Deficiency means continued action of elastase. Breaks down elastin in alveoli== emphysema
Long term protein regulation?
Changing gene expression
Can change rate of protein synthesis through enzyme induction or repression
Can change rate of protein degradation through ubiquitous proteosome pathway
Important point about clot formation?
It is an amplification cascade
Role of g-carboxyglutamate residues in clot formation?
Responds to calcium present at site of damage. Brings clotting factors site
Structure of fibrinogen?
Has negative charges and globular units at ends to prevent aggregation
What causes classic haemophilia?
A defect in factor VIII of the clotting cascade
What is interesting about thrombin in the clotting cascade?
It makes the cascade a feed forward mechanism
How is clotting process stopped?
Dilution of clotting factors by blood flow and removal by liver
Digestion by proteases
Specific inhibitors
What points of blood clot formation can be regulated?
Inactive zymogens low concentration
Proteolytic activation
Amplification (signal cascade)
Clustering of factors at damage site
Feedback activation by thrombin
Termination of clotting mechanisms
Clot breakdown controlled by proteolytic activation
Regulating enzyme activity?
Short term:
Substrate and product concentration
Changing enzyme conformation (allosteric, covalent modification, proteolytic cleavage)
Long term regulation
Change rate of protein synthesis and degradation
What drug works on the clotting cascade?
Warfarin- prevents blood clots
