Enzyme 2 Flashcards
What are the four ways you can control enzyme activity?
Alter temperature
Alter chemical conditions eg pH
increase or decrease transcription or breakdown
Direct regulation of the enzyme molecule
What is cooperativity?
substrate-binding to one site increase affinity at another
An allosteric activator shifts the V [S} graph to the ….
shifts to the left
in the classic enzyme graph shape
An allosteric inhibitor shifts the V [S] graph to the ….
What is the new shape of the graph?
shifts to the right
new shape is sigmodal
What is Vmax for an allosteric inhibitor and activator compare to an average enzyme
Allosteric inhibitor has a lower Vmax
Allosteric activator has a higher Vmax
What is the effect of temp on V?
Draw a graph to explain this.
There is a slow increasing gradient.
There is an optimum temperature and after this the graph drops off fast.
What is the effect of pH on V?
Draw a graph to explain this.
pH graph looks like a mountain and it gets shifted to the left or to the right.
What is the effect of [Enzyme] on V
Explain via a graph
Positive gradient line through the origin
Remember Vmax= kcat x [E]
What are the two types of covalent enzyme regulation?
1) cleavage of peptide chain in zymogen
2) phosphorylation
Is the cleavage of peptide chain in zymogen reversible?
No
Is phosphorylation reversible?
yes
What is two non covalent method of enzyme regulation?
Reversible binding of molecules to specific sites
Increase or decease activity
State the equation to find the inhibition factor
If= 1+ [I] / Ki
Irreversible inhibitors include suicide substrates.
Name an example
aspirin
penicillin
Competitive inhibitors block what?
the binding between E + S and ES
Non-Competitive inhibitors block what?
the catalysis between ES and E + P
What do these inhibitors bind to?
Competitive
Uncompetitive
Non-Competitive
Competitive- Binds to only free E
Uncompetitive- Binds to only ES
Non-Competitive- Binds the either
What is the equation for V including IF for competitive inhibitors?
V= Vmax x[S] / (Km xIf) + [S]
What is the equation for V including IF for non competitive inhibitors?
V= (Vmax/If) x [S] / Km + [S]
What is the equation for V including IF for uncompetitive inhibitors?
V= Vmax x[S] / Km +([S] xIf)
X= 1/[S] y= 1/v
What does the line look like for a uncompetitive inhibitor?
Straight line to the left of the original line / /
V max seems to be smaller
Km seems to be smaller
X= 1/[S] y= 1/v
What does the line look like for a competitive inhibitor?
Inhibitor line crosses the other at the y intercept
Vmax is the same
Km seems to be larger
X= 1/[S] y= 1/v
What does the line look like for a noncompetitive inhibitor?
Inhibitor line crosses the other on the x axis
V max is smaller
Km is the same
What do mixed inhibitors bind to ?
Do the lines on the 1/v 1/[S] cross?
Binds to either but different affinity to E and ES
Lines cross but not on axis
Name an example of the use of competitive and non competitive inhibitors?
Competitive= Viagra statins
Non competitive= Turmeric
What are the 2 types of multiple substrate/product reactions?
Sequential Method- ordered or random
E+A+B - EAB- ECD-E+C+D
Pingpong method- covalent bonds are formed
EA-EC - C or E+B - EB
What are the 4 general enzyme strategies?
1) Position the reactants correctly 4 interactions
2) Distort reactants so less stable
3) Stabilise transition states
4) Change environment to favour the reaction
Can environmental conditions and inhibitors affect activity?
Yes
