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BIOC192 > 10 > Flashcards

10 Flashcards

1
Q

Where does enzyme substrate binding occur

A

Active site

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2
Q

How does the active site bind to substrate

A

Active sitre bind to substrates via several weak interactions

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3
Q

What determines the specify of the reaction

A

The active site

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4
Q

What do many weak interactions ensure

A

Specificity and reversablitly

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5
Q

Contridion for weak bonds to form

A

Weake bonds can only form if real ent atoms are precisely postitioned

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6
Q

It is ____ to break weak bonds

A

It is easier to break weak bonds

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7
Q

Molecular ______ between ___ and ____ is critical

A

Molecular complementarity between exhume and substrate is critical

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8
Q

Enzymes show

A

Geometric and stereospecififity

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9
Q

Two models for enzyme-substrate binding

A

-Locke and key
- induced fit

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10
Q

Provided the ____ of the ____ _____ is _____, the enzyme can ______ between ______ groups on the _______

A

Provided the shape of the active site is asymmetric, the enzyme can distinguish between identical groups on the substrate

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11
Q

Ezymes are _____ not. _____

A

Dynamic not static

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12
Q

Types on enzyme substrate bonds

A
  • ionic bonds
  • hydrogen bonds
  • van der walls interations
  • covalent bonds
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13
Q

Ionic bonds (salt bridges)

A
  • uses charges side chains (Asp,Blu,Arg,Lys)
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14
Q

Hydrogen bonds

A

Side chain or backbone O and N atoms can often act as hydrogen bond acceptors and donors

(Only happen when two groups are in correct orientation)
(- connections between substrates and active site redidues within enzymes)

  • need side chains for diversity
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15
Q

Van der walls interactions

A

Between any protein and substrate atoms in close proximity: weakest of all interations

Not much specificity

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16
Q

Weakest interactions

A

Van der walls

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17
Q

Example of realises weak interactions and covalent interations

A
  • ionic bonds
  • hydrogen bonds
  • van der walls interactions
  • covalent
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18
Q

Covalent bonds

A
  • between active sites and amino acid side chains
  • relatively rare - much stronger then other bonds
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19
Q

What happens when hexokinase binds a substate

A

Conformational change

20
Q

3 wats active energy is lowered

A
  1. Groundstate destabilisation (trough up)
  2. Transition state stabilisation (trough down)
  3. Alternate reaction pathway with a different “(or lower energy) transition state

1 and 2 can be achieved the same way: by having an active sire that has shape/charge complementarity to the TS, not the substate

21
Q

Catalytic mechanisms (common to all enzymes vs specific to reaction pathway)

A
  1. Preferential binding of the transition state
  2. Proximity and orientation effects
  3. Acid-base catalyst
  4. Metal ion catalysis
  5. Covalent catalysis
22
Q

How prefectural binding of the transistor state happens

A

An enzyme bind the transition state more tightly then it binds the substate
Transition states are transient and cannot be isolated (they are very high energy) —> need to design and synthesise an analogue

An analogue is something the looks like the transition state but cannot be turned into a substrate

23
Q

Enzymes catalyse thrermodyntmaclly favourable reactions

A

by lowering the activation enenery

24
Q

Transition state shit - maybe go over this

A
25
Q

transition state analogues as drugs - how?

A

Lipitor = powerful cholesterol-lowing drug
- it inhibits HMG-CoA reductase (within the biosynthetic pathway for chlolesterol)
- Liptor is a transition state analogue of the HMG-CoA reductase reaction pathway
- Lipitor looks more like the transition state so it binds to active site

26
Q

If you want an inhibitor…

A

Use something that looks like the transition state

27
Q

How transition state analogues are good drugs

A
  • enzymes are often targets for drugs and other beneficial agents
  • transition state analogues often make ideal enzyme inhibitors
28
Q

What does analapril and aliskiren do?

A
  • lower blood pressure
29
Q

What do statins do?

A

Lower serum cholesterol

30
Q

What are protease inhibitors?

A

AIDS drugs (transition state analogue of transition state hiv proteases)

31
Q

What is a Juvenile hormone esterase

A

A pesticide target (

32
Q

What is Tamiflu ?

A

An inhibitor of influenza neuraminidase (transition state

33
Q

For two molecules to react they need to be

A
  • close together (proximity)
  • in the correct orientation
34
Q

The reaction hexokinase catalyses and how it shows probity and orientation hexokinase is enabling through chemical reaction

A
  • taking a phosphate off an atp and put onto glucose
  • hexokinase has evolved An active site that binds glucose in its complementary way and also bind ATP adjacelntly with its phosphate group postitoned at its perfect place to be transferred onto the hydroxyl of the glucose
35
Q

What does acid-base catalysis involve?

A

Proton H+ transfer (must have side chains that can exchange protons
- end=zyems with these residues in their active sites might have high or low activity depending on the pH of the solution and the environment at the active site

36
Q

Which amino acid is particularly suitable to acid base reactions?

A

Histidine

37
Q

Why is histidine so suitable for acid base reactions

A
  • pKa (his) ~ 6.5 (close to physiological pH)
  • depending on the environment of the active site, his can dontate or accept a proton
38
Q

At least a third of known enzymes require ____ _____ for catalytic activity

A

Metal ions

39
Q

Metal ions provide:

A
  • substrate orientations -> due to their specific coordination geometry
  • ability to act as a Lewis acid (electron acceptors) to polarise H2O molecules or other functional groups
  • sites for electron transfer ( redox reactions)
40
Q

Metal ions may be ______ at active enzyme sites

A

Cofactors

41
Q

Hexokinase uses ___ as a cofactor

A

Mg2+

42
Q

At the active site of hexokinase - diagram

A
43
Q

What does Mg2+ do in the active site of hexokinase

A

Mg2+ ion balances negative charge of the transition state

44
Q

What is covalent catalysis?

A
  • involves the formation of a reactive, short-lived intermediate, which is covalently attached to the enzyme
  • can have a nucleophillic side chain form a short lived intermediate which is covalent with the substrate
  • b gets cleaved off
  • water can then atack that bond and A is also then cleaved
45
Q

The enzyme - substrate interaction relies on

A

multiple, weak interactions and (often) induced fit

46
Q

Ezymes preferentially bind and ______ the _____ ______

A

Enzymes preferentially bind and stabilise the transition state

47
Q

There are a variety of _____ _____, for providing alternate reaction routes compacted to the ________ ______

A

There are a variety of catalytic mechanisms,for providing alternate r reaction routes compared to the uncatalysed reaction

BIOC192 (38 decks)

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