BC 10 Enzymes

Question 1

holoenzyme

Answer 1

catalytically active enzyme, including all subunits, and cofactors
apoenzyme (inactive)+cofactor=active (holoenzyme)

Question 2

Enzyme Naming

Answer 2

Substrate + Ase
substrate + function + ase (lactate dehydrogenase)
exceptions: trypsin, pepsin, chymotripsin, thrombin

Question 3

How are enzymes different from ordinary chemical aspects

Answer 3

1. higher reaction rates compared to uncatalyzed
2. mild reaction conditions, atmospheric pressure and neutral pH, ambient Temp
3. Great specificity
4. capacity for regulation, responds to cell needs

Question 4

cofactor

Answer 4

small molecule required for catalytic activity

can be organic, coenzyme: vitamins

can be metal ion: Cu2+ Fe3+ Zn2+

cosubstrateL only transiently associated with given enzyme

Question 5

prosthetic group:

Answer 5

cofactor that is permanently associated with protien ie: heme is prosthetic to hemoglobin

Question 6

active site

Answer 6

often not contiguous with primary sequence but made by tertiary and quarternary structures

Question 7

ezyme binding

Answer 7

lock and key: outdated
induced fit: banding of substrate at active site distors both the enzyme and substrate, the active site becomes complimentary to substrate only AFTER it is bound.

Question 8

enzyme specificity

Answer 8

functional group specificity: chymotrypsin (phynylalanine) trypin (lysine) Elastase (Glycine)
Also, glucokinase, can bind glucose, not galactose (epimers)

stereospecifity: lactate dehydrogenase only binds with L lactat not with D lactate.

Question 9

binding energy

Answer 9

created by formation of multiple weak non covalent interactions between substrate and enzyme during transition state, forms additional bonds as it enters transition state

enzymes often more complementary to transition state. stabilizes transition state and accelerates rate of reaction

Question 10

Antibiotics

Answer 10

glycopeptidyl transferase (GT) enzyme reguired by bacteria for cell wall construction. Penicillin binds to GT preventing cell wall construction. (covalently attaches serine to active site of GT. Inactivates enzyme.

Question 11

Enzyme Catalysis

Answer 11

1. Catalysis by proximity: higher concentration, the more frequently they encounter
2. Covalent catalysis: enzyme forms transient covalent bond with substrate. (coenzymes involved, and tranferases)
3. Catalysis by strain: catalyze lytic reactions (breaking covalent bonds) bind in conformation that weakens the bond, vulnerable to cleavage.
4. Acid/Base Catalysis: ????

Question 12

Rate of enzyme catalyzed reaction

Answer 12

Factors affecting:
Concentration: substrateL rate will increase until vmax
Enzyme concentration: will keep increasing
pH: reactive groups need to be protonated or unpotonated. pH can greatly affect activity. Each enzyme optimal pH
Denaturation: temp, pH , metal ions, becomes unfolded. Irreversible and total loss in fxn.
Temp: small increase will increase kinetics.obtimal between 35-40