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Co-factors
- -requirement of some enzymes for full activity
- -inorganic ions (Mg2+, Fe2+, etc.)
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Co-Enzymes
- -requirement of some enzymes for full activity
- -organic molecules (Vitamins)
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prosthetic group
A co-enzyme or co-factor that is tightly associated(permanently) with the enzyme
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Holoenzyme
Apoenzyme + Required Co-factor/Co-enzyme
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Apoenzyme
The protein component of an enzyme, to which the coenzyme attaches to form an active enzyme.
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Oxidoreductases
Transfer of electrons (hydride ions or H atoms)
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Transferases
Functional Group transfer reaction
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Hydrolases
hydrolosis reaction (transfer of functional group to water)
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Lyases
addition of groups to double bonds, or formation of double bonds by removal of groups.
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Isomerases
transfer of groups within molecues to yield isometric forms
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Ligases
formation of c-c, c-s, c-o and c-n (covalent) bonds by condensation reactions coupled to ATP cleavage
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Catalysts: 3 features
- -lower the amount of energy required for a reaction to proceed
- -speed up attainment of equilibrium but do not change equilibrium
- -are unchanged by the reaction; recycled to participate in another reaction
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Enzymes vs Chemical Catalysts
4 points
- 1) Faster
- 2) Milder conditions
- 3) Greater specificity
- 4) Potential to be regulated
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Substrate (S):
the molecule to be actedupon by the enzyme
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equation for velocity
V= k[S]
- k- rate constant
- [S]- concentration of substrate
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What is the relationship between the rate constant and the free energy of the transition state
inverse and exponential
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What is the main physical limitation on reaction speed of an enzyme
Rate of difusion
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The two Binding Effects an enzyme can have on a substrate
- 1) Substrate Binding (proximity effect)
- 2) Transition-state Stabilization
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Proximity Effect of Enzyme:
5 steps
- (1) Reduces the entropy (decreased freedom of motion of two molecules in solution).
- (2) Desolvation of the substrate to expose reactive groups
- (3) Alignment of reactive functional groups of the enzyme with the substrate
- (4) Distortion of substrates
- (5) Induced fit of the enzyme in response to substrate binding
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Transition-state analogs
stablecompounds whose structures resemble unstable transition states. Used as a enzyme inhibitor. (active site blocker)
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Catalytic antibodies
antibodies evoked by man made antigens (Transition state analogs) that have specific catalytic capabilities towards a targeted molecule.(TS analog will mock the targeted molecules TS state)
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the two types of chemical catalysis by enzymes
- 1)Acid/base Catalysis
- 2)Covalent Catalysis
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what are the two main feature of Acid base Catalysis
- -Reaction acceleration is achieved by catalytic transfer of a proton to or from side chain Aminos of enzyme (histidine is important in this way)
- -at end of reaction the amino must be returned to original protonated state
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In covalent catalysis how is group X transfered from subrate A to substrate B?
A-X + Enz X-Enz + A
X-Enz + B B-X + Enz
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