ENZYMES AND ENZYMOLOGY

Question 1

what is enzymology?

Answer 1

the pure and applied study of enzymes, a sub-discipline of biochemistry

Question 2

what is zymology?

Answer 2

the applied study of process fermentation, a sub-discipline of biotechnology and industry microbiology.

Question 3

what is a zymogen (aka proenzyme)?

Answer 3

an inactive protein that can break apart/change
to yield an active enzyme

Question 4

what is catalysis?

Answer 4

-enzymes are proteins that are catalysts
- catalysts increase the rate of a reaction and is not consumed by reaction

Question 5

what are controlled catalytic coupling?

Answer 5

• metabollic conditions are not thermodynamically favoured.
• but can be made by pairing with enzymes that are

Question 6

example?

Answer 6

• D-(+)-glucose + Pi → D-glucose 6-phosphate + H+
  is not thermodynamically viable
  but:
• D-(+)-glucose + ATP4- → D-glucose 6-phosphate + ADP3- + H+
  is viable and can be
  catalysed by hexokinase

Question 7

how enzymes work?

Answer 7

• enzymes can be expressed or not expressed in a cell.
• some enzymes can be turned on or off = post - translational regulation.
• only low concentration is needed.
• rate constant of the reaction is proportional to enzyme conc.
• enzyme does not change the equilibrium of the reaction.

Question 8

what is EC 1.x.x.x number?

Answer 8

oxidoreductases

Question 9

EC 2?

Answer 9

transferases

Question 10

EC 3?

Answer 10

hydrolases

Question 11

EC 4?

Answer 11

lyases

Question 12

EC 5?

Answer 12

isomerases

Question 13

EC 6?

Answer 13

ligases

Question 14

EC 7?

Answer 14

translocases

Question 15

what are isoenzymes?

Answer 15

if many enzymes catalyse same reaction but have different structures, they have same EC number.

Question 16

what is a holoenzyme?

Answer 16

enzyme that has all of protein subunits together.
- without prosthetic groups it would be the apoprotein.

Question 17

what are cofactors?

Answer 17

• stuff bound to an enzyme to raise catalytic capability above that provided by just amino acyl sidechains alone.

Question 18

what are prosthetic groups?

Answer 18

• either solely organic or tightly bound metals in organic frames.
• denaturation will remove them
• undergoes reversible changes in oxidation sate.

Question 19

what is enzyme function: the Michaelis kinetic?

Answer 19

• substrate = S; product = P; enzyme = E
• S + E ↔ SE ↔ PE → P + E

Question 20

what is the lock and key hypothesis? (1894)

Answer 20

• substrate fits directly into active site. therefore reaction is very specific.

Question 21

induced fit hypothesis? (1959)

Answer 21

active site is not perfect fit to substrate and substrate induces a change in shape of enzyme

Question 22

what is gibbs energy?

Answer 22

• measure of thermodynamically flavouribility.
• if a reaction has negative gibbs energy, releases energy.
• if reaction is positive = takes energy.

Question 23

what is activation energy? ΔG‡

Answer 23

• thermodynamically favourable reactions need to overcome activation energy.
• rate of reaction is determined by magnitude of G
• enzymes can change reaction rate by lowering G

Question 24

how is ΔG‡ lowered?

Answer 24

H2O2 molecule is bound at one end to the heme B
iron atom and by hydrophobic interactions with 3
amino acyl residues and the ‘frame’ of the heme B.

Question 25

what are serine proteases?

Answer 25

• active site contains a serine residue that acts as nucleophile, donating an electron pair.
• catalyses the hydrolyses of peptide bonds

Question 26

what are examples of serine proteases?

Answer 26

• chymotrypsin
• trypsin
• elastase

Question 27

what is trypsin?

Answer 27

• positively charged amino acyl residues - lysine and arginine

Question 28

what is chymotrypsin?

Answer 28

hydrophobic amino acyl residues - tyrosine, phenylanine, tryptophan

Question 29

what is elastase?

Answer 29

valine, alanine, glycine

Question 30

what is stereospecificity?

Answer 30

• 3 points of contact needed therefore only one enatiomer will fit

Question 31

formula for michealis kinetic?

Answer 31

enzyme rate = maximum activity x conc substrate / michealis constant x conc. substrate