ENZYMES AND ENZYMOLOGY Flashcards
what is enzymology?
the pure and applied study of enzymes, a sub-discipline of biochemistry
what is zymology?
the applied study of process fermentation, a sub-discipline of biotechnology and industry microbiology.
what is a zymogen (aka proenzyme)?
an inactive protein that can break apart/change
to yield an active enzyme
what is catalysis?
-enzymes are proteins that are catalysts
- catalysts increase the rate of a reaction and is not consumed by reaction
what are controlled catalytic coupling?
- metabollic conditions are not thermodynamically favoured.
- but can be made by pairing with enzymes that are
example?
- 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
how enzymes work?
- 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.
what is EC 1.x.x.x number?
oxidoreductases
EC 2?
transferases
EC 3?
hydrolases
EC 4?
lyases
EC 5?
isomerases
EC 6?
ligases
EC 7?
translocases
what are isoenzymes?
if many enzymes catalyse same reaction but have different structures, they have same EC number.
what is a holoenzyme?
enzyme that has all of protein subunits together.
- without prosthetic groups it would be the apoprotein.
what are cofactors?
- stuff bound to an enzyme to raise catalytic capability above that provided by just amino acyl sidechains alone.
what are prosthetic groups?
- either solely organic or tightly bound metals in organic frames.
- denaturation will remove them
- undergoes reversible changes in oxidation sate.
what is enzyme function: the Michaelis kinetic?
- substrate = S; product = P; enzyme = E
- S + E ↔ SE ↔ PE → P + E
what is the lock and key hypothesis? (1894)
- substrate fits directly into active site. therefore reaction is very specific.
induced fit hypothesis? (1959)
active site is not perfect fit to substrate and substrate induces a change in shape of enzyme
what is gibbs energy?
- measure of thermodynamically flavouribility.
- if a reaction has negative gibbs energy, releases energy.
- if reaction is positive = takes energy.
what is activation energy? ΔG‡
- 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
how is ΔG‡ lowered?
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.
