Enzymes I Flashcards
1
Q
describe enzymes
A
- Enzymes are soluble proteins that act as catalysts and increase the rate of chemical reactions
- Enzymes accelerate reactions at human body temps and at pH conditions found in cells
- Provide a means for regulating the rate of metabolic pathways in body
2
Q
what are the 2 names of enzymes
A
- The short recommended name has the suffix “-ase” and is mainly describing the reaction that is carried out
- The systematic name follows a classification that includes a name and an Enzyme Commision (EC) number
- 6 major classes
3
Q
properties of enzymes?
A
- Active site: relatively small part of the a 3D pocket or cleft formed by AA
- Catalytic efficiency: enzymes ranges from 103-108 times faster than uncatalyzed reactions
- The specificities of enzymes are very high
- Recognition of optical config of the substrates
4
Q
name the cytosolic pathways that use enzymes
A
- Glycolysis
- Gluconeogenesis (liver and kidney)
- Pentose-phosphate Pathway (PPP) also named Hexose-monophosphate pathway (HMP)
- Fatty acid de novo synthesis
- Cholesterol synthesis
- TAG synthesis
5
Q
name the mitochondrial pathways that use enzymes
A
- Pyruvate dehydrogenase complex (PDH)
- citric acid cycle/Krebs Cycle
- ETC and oxidative phosphorylation
- Fatty acid B-oxidation
- Ketone body synthesis (liver only, fasting)
6
Q
how do enzymes function?
A
- All reactions have to go through a transition state
- Enzymes can stabilize the transition state
- Enzymes provide an alternate reaction pathway and as a result can reduce the energy of activation
- Enzymes do not change the ΔG of the overall reaction
7
Q
describe enzyme kinetics
A
- The study of velocity (product formation) under specific conditions:
- different substrate concentrations
- different pH
- different temps
- Enzyme kinetics can also include the addition of drugs
- Enzyme kinetics offer insight into the affinity of the enzyme for different substrates and also for drugs
8
Q
effect of substrate concentration on the velocity?
A
- Velocity represents the product formation over time
- Velocity increases at higher substrate concentration for any enzymatic catalyzed reaction until Vmax is reached
- At Vmax, all available binding sites on the enzyme molecules are saturated
9
Q
effect of temp. on velocity
A
- The velocity increases with higher temp.
- Except when the temp rises above 40 C, which causes human enzymes to be denatured
10
Q
effect of pH on velocity
A
- The concentration of protons affects the reaction velocity
- An extreme pH can denature the enzyme
- Different enzymes can have different optimal pH
- Pepsin cleaves dietary proteins and acts in the lumen of stomach under acidic conditions
- Trypsin cleaves dietary proteins in the duodenum
- Alkaline phosphatase cleaves phosphate groups from nucleotides and proteins and forms an alkaline pH
11
Q
name the MM kinetics equation
A
12
Q
describe the Lineweaver-Burk Plot
A
- Less measured points will result in a straight line instead of a hyperbolic cuve (double-reciprocal plot)
- Vmax and Km (which are obtained from 1/Vmax and -1/Km) are found at the intercept with the:
- y-axis represented as 1/Vmax
- x-axis represented as -1/Km
- slope is Km/Vmax
13
Q
A
14
Q
contrast small Km vs large Km
A
- Small Km for enzyme 1 reflects a high affinity of enzyme for the substrate
- Large Km of enzyme 2 reflects a low affinity of enzyme for the substrate
15
Q
describe competitive reversible inhibition
A
- A competitive reversible inhibitor can be a structural analog of the substrate
- Statins inhibits HMG CoA reductase, the regulated enzyme of cholesterol synthesis
- The drug competes with the substrate for the binding to the active site
- Instead of Enzyme-Substrate, Enzyme-Inhibitor is formed
19
Q
describe the kinetics of noncompetitive inhibition
A
- The apparent Vmax is smaller when compared to the uninhibited reaction whereas the Km is the same
