Enzymes Flashcards
Covalent catalysis
Enzyme temporally covalently bonds to the substrates and acts as “electron sink” or “carrier”; it carries the electron for a moment
Acid Base Catalysis
Move H+ electron
Spacial Enzyme
Increases the likely hood of successful collisions
Electrostatic
Use metal or charged ions that helps stabilize some other species
Substrate
Molecule upon which an enzyme acts
Active site
Location within enzyme where substrate is held during chemical reaction; site of catalysis
Lock and key theory
Enzyme active site (lock) already in appropriate confirmation for substrate( key) to bind. Enzyme and substrate complementary
no alterations in 3D or 4D confirmation
Induced fit
Enzyme and substrate go conformational changes to interact fully
Substrate changes to fit the shape of the enzyme
Apoenzyme
Enzymes without cofactors
Haloenzymes
(have)
Enzymes that have cofactors
Fat soluble vitamins
DAKE
Cofactors
Inorganic molecules or metal ions
- ingested as dietary minerals
Ex: DNA polymerase uses Mg2+ as cofactor
Coenzymes
Small organic groups or carriers
vitamins such as NAD+ or FAd, CoenzymeA
At saturation
Enzyme working at its maximum velocity called vmax
What is the only way to increase vmax
increase enzyme concentration
Rate of reaction (V)=
Vmax [S]/ (km + [S])
km=
the substrate concentration were Vo = 1/2 Vmax
lower km= better enzyme working
Kcat
Turnover number
How many substrates an enzyme can turn into products in 1 sec at max speed
Cooperativity
Have a sigmoidal curve
-Have multiple subunits and multiple binding sites
-Binding to one site increases the binding to other to other subunits
Example: Hemoglobin
Positive cooperativity
Substrate binding increases affinity for subsequent substrate (hemoglobin)
Negative Cooperativity
Negative-cooperatively - Substrate binding decreases affinity for subsequent substrates
Optimal Blood pH
7.4
Pepsin in stomach pH
2
Pancreatic enzyme in small intestine pH
8.5
Salinity
Salt concentration increasing= disrupt hydrogen and ionic bonds, causing changes in confirmation of the enzyme and even denaturization
Ideal body temp
37C, 98.6F, 310K
Competitive Inhibitor
Binding Site: Active Site
Impact on Km: Increases
Impact on Vmax: not changed
-increasing substrate concentration to overcome
Non-competitive
Binding Site:Allosteric Site causing confirmation changes in the enzyme
Impact on Km: Unchanged
Impact on Vmax: Decreases
Mixed
Binding Site:Allosteric Site or ES complex
Impact on Km: Increases or decreases
Impact on Vmax: Decreases
Umcompetitive
Binding Site:Allosteric Site only to ES complex and locks the substrate in the enzyme preventing its release
Impact on Km: Decrease
Impact on Vmax: Decreases
Regulated Enzyme
Allosteric Enzyme
Covalent (reversible)
Enzyme itself
“ACE”
Allosteric Enzyme
Regulator binds to the non-active site, and it activates/inactivates/inhibits the enzyme
-multiple binding sites
Covalent (reversible) Modified enzymes
Enzymes can be activated by phosphorylation or dephosphoralation
- ex :Glycosylation mainly refers in particular to the enzymatic process that attaches glycans to proteins,
Enzyme itself
Zymogens: are secreted in inactive form and are activated by cleavage (because they are dangerous if not controlled)
- irreversibly activated
- have an “-ogen” ending
ex: pepsinogen
