9. Enzyme Kinetics

Front 1

What are the 4 physical properties that we identify in enzymes?

Back 1

1. Composition
2. Cofactors used
3. Isoenzyme forms
4. Binding sites

Front 2

What are enzymes composed of?

Back 2

Proteins, organic components of C, H, O, N, S,.

Front 3

What is a catalyst?

Back 3

Substance that increases a reaction rate without being changed or consumed.

Front 4

What are cofactors?

Back 4

Nonproteins that optimize an enzyme's catalytic activity.

Front 5

What is a
-holoenzyme?
-apoenzyme?

Back 5

Holo = whole enzyme+cofactor
Apo = enzyme w/out cofactor

Front 6

What are
-Coenzymes?
-Activators?
-Prosthetic groups?

Back 6

Coenzyme: loose bound organic cofactor.
Activator: loose inorganic ion
Prosth. Grp: titely bound cofactor

Front 7

What are characteristics of isoenzymes?

Back 7

Different forms that catalyze same reaction; unstable; differentiate w/ electrophoresis
-CK and LD are examples

Front 8

What are the catalytic properties of enzymes?

Back 8

1. Effective in small amounts
2. Unchanged by the reaction
3. Decrease activation energy
4. Specific
5. Can lose enzyme activity

Front 9

What causes an enzyme to irreversibly lose its activity?

Back 9

Denaturation

Front 10

4 types of enzyme specificity:

Back 10

1. Absolute
2. Group
3. Bond
4. Stereo

Front 11

What are the 2 types of enzyme classifciations?

Back 11

1. Substrate based
2. IUB systematic

Front 12

How are enzymes classified in the old Substrate based method?

Back 12

Based on the type of SUBSTRATE the enzyme acts upon

Front 13

How are enzymes classified in the new IUB systematic method?

Back 13

Based on the catalyzed REACTION

Front 14

List the 6 enzyme classes in the IUB systematic method:

Back 14

1. Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases

Front 15

-Cite an oxidoreductase:
-Cite 4 transferases:
-Cite 3 hydrolases

Back 15

Oxidored: LD
Transfer: CK, AST, ALT, GGT
Hydrolas: Acid phosphatase, amylase, urease

Front 16

What are the 3 phases of an enzyme reaction?

Back 16

1. Lag phase
2. Linear phase
3. Substrate depletion phase

Front 17

What occurs in the lag phase?

Back 17

Mixing and temp/kinetic equilibrium establishment.

Front 18

What occurs in the linear phase?

Back 18

Constant reaction; the change in absorbance is constant per unit time - this is where we assay.

Front 19

What occurs in the substrate depletion phase?

Back 19

little change in absorbance/time

Front 20

What substrate concentration is seen in 1st vs. Zero order reactions?
How does the reaction rate relate to each order?

Back 20

1st order: low [S] - rate is proportional to amt of substrate

Zero order: high [S] - rate is independent of substrate

Front 21

Why is zero order reaction rate preferred to first order?

Back 21

Because the zero order reaction will produce a linear graph of the reaction and allow measurement of the enzyme.

Front 22

What is the definition of the michaelis menton constant?

Back 22

The [S] that gives 1/2Vmax.

Front 23

What is the substrate concentration used in clinical assays?

Back 23

10Km

Front 24

How does that Substrate conc. affect the Velocity? What order is the reaction? What happens to the Vmax?

Back 24

-Velocity approaches Vmax.
-Order is Zero
-Vmax becomes indepenent of [S]

Front 25

So what is the resulting rate of clinical, zero-order assays?

Back 25

>90% Vmax!

Front 26

What is the optimum pH for biologic reactions?

Back 26

7.8-8.2

Front 27

What temp are clinical enzymes measured at?

Back 27

Biological, 37

Front 28

On a lineweaver-burk plot:
-What is the y-intercept?
-What is the slope?

Back 28

Y-intercept = 1/Vmax

Slope = Km/Vmax

Front 29

So if a Km is increased but Vmax is unchanged, what happens to the plot?
-What type of inhibition is this?

Back 29

The slope increases but the y-intercept stays the same.
-Competitive inhibition

Front 30

If the Km is unchanged but the Vmax is decreased what happens to the plot?
-What type of inhibition is this?

Back 30

Slope increases AND the y-intercept increases.
-Noncompetitive inhibition

Front 31

What happens to a lineweaver burke plot when Vmax AND Km are decreased?
-What type of inhibition is this?

Back 31

The Y-intercept decreases but the slope stays the same.
-Uncompetitive inhibition