Amino Acids/Proteins

Question 1

AAs That Can Be Glycosylated

N and O

Answer 1

N- asparagine

O- serine and threonine

Question 2

Alpha Helix Dimensions

Answer 2

5. 4 angstroms per turn
6. 6 residues per turn
7. 5 angstroms rise/residue

Question 3

Beta Sheet Dimension

Answer 3

3.5 angstroms per residue

Question 4

Incretins

Answer 4

hormones that are released after food intake to regulate insulin release. Let’s the brain know that you don’t need to eat anymore, signals to gut for gastric emptying, signals to pancreas to increase glucose-dependent insulin biosynthesis, and to decrease glucagon secretion.

Question 5

Chymotrypsin catalytic triad includes ____ ____ ___ AAs. ___ removes proton from ____, creating potent nucleophile

The ____O- bonds to carbonyl of amide of protein, forming ________

The _____ stabilizes the ____

Answer 5

Chymotrypsin catalytic triad includes serine, his, and asp AAs. His removes proton from ser, creating potent nucleophile

The Ser-O- bonds to carbonyl of amide of protein, forming negatively charged tetrahedral intermediate

The oxyanion hole stabilizes the negative charge of the intermediate

Question 6

kCat

Answer 6

Vmax/[E]

• rate constant of ES to form products
• does not change with enzyme []
• ‘Turnover number’
• affected by pH and temp

Question 7

Km

Answer 7

• specific to enzyme-substrate pair, enzyme can have different Kms depending on different substrates
• dependent on rxn conditions, such as pH and temp
• usually close to physiological substrate concentration(nanomolar to millimolar)

Question 8

Catalytic efficiency

Answer 8

Kcat/Km or Vmax/Km
-used to estimate: substrate preference, compare activities under certain conditions

-the higher the Kcat/km, the bettet the substrate/catalytic efficiency of enzyme

Question 9

Isozymes

Answer 9

• have different primary structure but catalyze same chemical rxn and act upon same substrate
• have different Kcat and Km and different temp and pH dependencies
• thought to have evolved from divergence and gene duplication

Question 10

Cardiac Enzymes Analyzed For Suspected MI

Method used for analysis

Answer 10

Troponin-I/T, CK-MB, Myoglobin

ELISA

Question 11

How did scientists show that MDM-2 and P53 interact?

Answer 11

Co-immuno ppt

Question 12

MDM2

Answer 12

Oncoprotein, E3 Ub-ligase which promotes p53 ubiquitination in response to cellular stress

Question 13

Relationship between V and [E]

Answer 13

Rate of rxn is directly proportional to [E] and [S].

Example: if [E] is halved, the initial V of rxn, as well as Vmax, are reduced to half of the original.

Question 14

When is an enzymatic rxn 1st order? 0th order?

Answer 14

1st order when [S]«»Km

Question 15

Lineweaver Burke Equation

Answer 15

1/Initial V= Km/Vmax[S] + 1/Vmax

X intercept is -1/Km
Y intercept is 1/Vmax

Question 16

Competitive Inhibition

____ Vmax
____ Km

1/Vmax on LB plot ______
-1/Km on LB plot ______

Answer 16

Doesn’t change Vmax
Increases Km

1/Vmax on LB plot does not change
-1/Km on LB plot moves to the right

Question 17

Noncompetitive Inhibition

____ Vmax
____ Km

1/Vmax on LB plot ______
-1/Km on LB plot ______

Answer 17

Decreases Vmax
Doesn’t change Km

1/Vmax on LB plot shifts up
-1/Km on LB plot remains the same

Question 18

Homotropic effector

Answer 18

When actual substrate of enzyme can also act allosterically. Can be positive or negative effector.

Have sigmoidal curves.

Question 19

Heterotropic effectors

Answer 19

When effector is different from enzyme’s substrate.

• Usually used in feedback inhibition of a multi-step pathway. End product can bind allosterically to enzyme.
• PFK-1 example, inhibited by citrate.