Biochem Block 1: Enzymes X 2 Lectures (Bondarenko)

Front 1

RNA molecules that act like enzymes are called

Back 1

ribozymes

Front 2

# of substrate molecules converted to product per enzyme molecule per second =

Back 2

turnover number

Front 3

Define holoenzyme

Back 3

The "whole" enzyme, including cofactors

Front 4

Define apoenzyme

Back 4

the PROTEIN COMPONENT of a holoenzyme

Front 5

A loosely bound cofactor to an enzyme is called a

Back 5

coenzyme

Front 6

A tightly bound cofactor to an enzyme is called a

Back 6

prosthetic group

Front 7

Many coenzymes are derivatives of

Back 7

vitamins

Front 8

Proenzymes are

Back 8

inactive precursors of enzymes...are activated by cleaving off extra sequences

Front 9

Remember, enzymes ______ energy of activation but do not change ____

Back 9

-lower

-free energy difference between reactants and products

Front 10

Enzymes can speed up a reaction by doing what actions to the enzyme substrate complex?

Back 10

-stabilize transition state complex
-form covalent intermediate
-destabilize leaving groups

Front 11

Why is substrate denatured?

Back 11

protein substrates are bulky and cannot fit into the active site. chymotrypsin must hydrolyze peptide bond on the carbon side of Phe, Tyr, or Trp so that the substrate can fit.

Front 12

Chymotrypsin hydrolyzes Phe, Tyr, or Trp. What do these enzymes have in common?

Back 12

They are all aromatic

Front 13

What amino acids make the catalytic triad?

Back 13

Aspartate-Histidine-Serine (D-Y-S)

Front 14

What amino acid is in the active site of gastric protease pepsin?

Back 14

aspartate

Front 15

Functional vitamin deficiency

Back 15

failure in transport system, inhibition of coenzyme synthesis

Front 16

which class of coenzymes forms a covalent bond with the substrate?

Back 16

activation-transfer coenzymes

Front 17

Thiamine pyrophosphate is a activation-transfer coenzyme that is used to cause _____________ reactions. thiamine deficiency is known as ___

Back 17

decarboxylation (breaking C-C bonds)

beriberi

Front 18

PLP forms covalent interactions with ____________.

Back 18

amino acids

Front 19

Sulfhydryl group of CoA forms

Back 19

thioesters

Front 20

Biotin activates and transfers ___________ in __________ reactions

Back 20

CO2, carboxylation

Front 21

Oxidation-reduction coenzymes work with oxidoreductase enzymes. Examples include

Back 21

NAD+, FAD

Front 22

Do oxidation-reduction coenzymes form covalent bonds with substrates?

Back 22

NO

Front 23

Alcohol dehydrogenase oxidizes ethanol while its coenzyme, NAD+, gets reduced. ______________ is a product of ethanol oxidation and is responsible for alcoholic hepatitis.

Back 23

acetaldehyde

Front 24

Metal ions help bind coenzymes to the enzyme by binding their _________. ________ is usually bound to the enzyme through metal ions. They also bind anions.

Back 24

-phosphate groups

-ATP

Front 25

Sarin gas is a ___________________ of acetylcholine esterase.

Back 25

covalent inhibitor

Front 26

Aspirin is a __________ of cyclooxygenase (COX), an enzyme involved in prostaglandin synthesis

Back 26

covalent inhibitor

Front 27

Penicillin is a ______________ that binds tightly to the enzyme necessary to form cell walls in bacteria, more tightly than any substrate or product can.

Back 27

transition state analog

Front 28

Allopurinol is a ______________ that binds tightly to xanthine oxidase to decrease urate production and thus treat gout

Back 28

transition state analog

Front 29

Heavy metals are toxic because they bind to the __________ or _______of many enzymes.

Back 29

SH groups
or
functional metal ions

Front 30

Michaelis-Menten equation:

Back 30

Vi: Vmax [S] / (Km + [S])

Front 31

Km is the....

Back 31

substrate concentration at half of the max velocity

Front 32

An enzyme with a small Km has a ______________ for that substrate

Back 32

high affinity

Front 33

An enzyme with a large Km has a ___________ for that substrate

Back 33

low affinity

Front 34

In the Lineweaver and Burk plot, the x intercept can be used to find Km. How?

Back 34

x intercept = -1/Km

Front 35

In the Lineweaver and Burk plot, the y intercept can be used to find Vmax. How?

Back 35

y intercept = 1/Vmax

Front 36

Why does hepatic glucokinase have a high Km?

Back 36

high Km = low affinity of glucokinase for glucose. That means you need large amounts of glucose for glucokinase to be effective. This is good in the liver because when you have high glucose, glucose gets phosphorylated into G6P and used by cells. When you have low amounts of glucose, you don't want cells to use up the remaining glucose. You want to increase blood sugar levels (glucose levels), not G6P levels. So hepatic glucokinase won't have a high affinity for glucose at low glucose concentrations (high Km).

Front 37

Why does hexokinase have a low Km?

Back 37

RBC has a high affinity (low Km) for hexokinase w/glucose because you need glucose to be metabolized to G6P right away for use, even with low amounts.

Front 38

Reversible enzyme inhibitors form what kind of bonds?

Back 38

noncovalent

Front 39

Competitive inhibition can be counteracted by

Back 39

high substrate concentration

Front 40

competitive inhibitors of cholesterol synthesis are

Back 40

statin drugs

Front 41

With competitive inhibition, what happens to Km and Vmax?

Back 41

velocity max does not change. However, now that you need more substrate to reach Vmax, Km (half Vmax) is increased.

Front 42

If you add an inhibitor to an enzymatic process that causes Vmax to increase, what kind of inhibitor did you add?

Back 42

a competitive inhibitor

Front 43

Noncompetitive inhibitors bind to ___________ sites on the enzyme

Back 43

different

Front 44

With noncompetitive inhibition, whathappens to Km and Vmax?

Back 44

Vmax decreases significantly. Km is unchanged (adding substrate has no effect)

Front 45

Allosteric enzymes have sites where allosteric inhibitors or activators cause

Back 45

conformational changes to enzyme

Front 46

Allosteric enzymes usually consist of multiple subunits and exhibit ___________ binding.

Back 46

cooperative

Front 47

In cooperative binding, the _____________ model is based on high cooperativity with all-or-none global states...the ___________ model shows one-by-one binding causing conformational changes in each subunit

Back 47

-concerted

-sequential

Front 48

Allosteric regulators have some benefits over competitive/noncompetitive regulators:

Back 48

1. stronger effect
2. may act as activators because they don't occupy the active site
3. don't have to resemble substrate or product
4. fast acting

Front 49

When you phosphorylate an enzyme, the target amino acids for phosphorylation are

Back 49

Ser

Thr

Tyr

Front 50

Protein Kinase A (PKA) is activated by

Back 50

cAMP

Front 51

Gproteins and PKA are regulated by

Back 51

protein protein interactions

Front 52

Precursors of proteases are called

Back 52

zymogens

Front 53

Trypsinogen is a zymogen that is cleaved by enteropeptidase to form ___________, the active enzyme

Back 53

trypsin

Front 54

What is the blood clotting zymogen cascade?

Back 54

prothrombin > thrombin digests fibrinogen > fibrin > clot formation

Front 55

phospholipase Cβ

Back 55

G protein activation

Front 56

the phospholipase Cγ

Back 56

fat/glycogen storage, activated by insulin in addition to MAP pathway and GLUT-4 going to membrane (to allow more glucose to enter cell)