Enzyme - Catalysis Flashcards
Transistion State Analogues
These stabilise favoured transistion state geometry evolved in enzymes for catalysis.
What are TS Analogues?
High energy intermediates existing betwene the substrate and the products of the catalysis.
What is the first stage in enzymes catalysis?
Formaiton of the ES complex,
What does ES complex formation depnd on?
Diffusion, specificity within the active site, binding and catalysis
Activation Energy
This is a kinetic paramter being the energy of the transition for a given reaction relative to the intial state.
Where is activaiton energy important?
Energonic thermodynamically unfavourable reactions, requiring energy input.
Transistion State
THis is a local energy maximum along the reaction co-ordinate
Why are enzymes important?
Stabilisation of the transistion state, lowering activation enery
How can transistion state formation be thermodynamically described?
Reduction of the substrate free energy, where the transistion high energy state has molecules in an unstable conformation
Induced Fit Model
This was proposed by Koshland in 1958 to explain protein conformational changes in ES binding
What does the IFM describe?
Optimization of the interface with ES substrate formation
What do IFM CC result in?
Reorientation of AA through enzymatic changes from intermoleuclar interactions
Why is the transistion states dificult to reach/maintain?
Its instability, requiring chemical bond ormation/breaking.
What does AE measure?
Difference in energy of reactants to transistion state
How can transisiton state be described quantum mechanically?
Promotion of electrons to higher energy levels allowing formaiton of new chemical bonds
What isan example of a transistion state analogue?
Yeast aldolase
Aldolase
This catalyses reversible reaction of converting F16BP into DHAP and GA3P
What can analogues be used for?
Design inhibitors of it, identifying key functional groups and stereochemistry in the reaction to design a moleucle mimicing thease features.
Sterochemistry
This is the chemistry of 3D arrangement of atoms in molecules
What is an example of a TSA?
Phosphoglycolohydroxamate mimicing Enediolate transistion state
How is enediolate distinct from PGD?
PGD contains a hydroxamate group mimicing the intermediary, binding by covalent bond to the active site.
What are the Km of PGD transistion state analogue?
DHAP =4x10^-4M
PGD Ki =1x10^-8M
Km/K = 4X10^4
How does Zinc cofactors stabilise Enediol?
Co-ordination to the negative charge of the oxygen.
Adenosine Deaminase
THis is an enzyme of the purine metabolism which catalyse the irreversible deamination of adenosine and deoxyadenosine to ionsine and deoxyinosine
What does Adenosine Deaminase form?
A transistio nstate of adenosine with an inhibitory form purine ribonucleotide with a Km of 3x10^-5M and Ki of 3x10^-15M
Km/Ki = 1x10^8
How does Purine Ribonucleoside and Adenosine differ?
Purine Ribonucleoside contains a H instead of a H2N
