enzymes Flashcards
enzymes
protein catalysts bind substrates release products have more than one subunit cut out the opportunity to go the unctalysed way
modification of enzymes
they always return to original form: not used up by reaction
act as a point of regulation
in metabolic pathways
combined catalytic activities=control
short=energy or long-foetal dvmpt
problems
over or under expression can lead to cell dysfunction ( can be used to identify problems such s heart attacks)
Substrate-Binding Sites
Substrates bind to specific sites via interactions with enzyme’s amino acids
spatial geometry dictates specificity
active catalytic site
where the reaction occurs
different functional groups co-enzymes, metal ions, amino acid
residues
pH & Temperature Profiles:
Enzymes have a functional pH & temperature range - e.g. increased temperatures = reaction rate
but if you go too far denaturation (looses its actual functionality)
enzyme catalysed
e+s=ES=e+p
reaction equilibrium
do not alter position
accelerate it’s establishment
Lock & Key’ Model
Complementary 3-D surface that “recognises” the substrate
- substrate binds through hydrophobic, electrostatic
interactions & hydrogen bonds
- Binding can be prevented by steric hindrance (bumping in to each other)& charge
repulsion
induced-fit model
As substrates bind, enzymes undergo conformational change
side chains of amino acids
binding reactions increase
dynamic surface= can increase atp
active site
Cleft or crevice formed by polypeptide chain - 3D arrangement permits reacting substrates
to approach each other
substrate binding
conformational change
transition state
bonds become maximally strained
activation energy
difference between substrate and transition state complex enzymes decrease the activation energy
overall rate of reaction
determined by no. of molecules acquiring activation energy
Cofactors/Coenzymes
Catalytic properties often dependent on non-peptide molecules coenzymes synthesised from vitamins ( deficiencies in diet=problem)
highly bound cofactors
prosthetic groups’
- e.g. Mg2+, Fe2+, Zn2+
metal ions
act as electrophiles (electron-attracting groups)
act in substrate binding or stabilise anions accept or even donate electrons in oxidation-reduction reactions
pH & Temperature Optima
Human enzymes function optimally at 37 ο C - Increasing temp from 0 -> 37 ο C increases
reaction rate
higher=denaturation losss of 2 and 3 structure
Isoenzymes
different amino acid sequence but catalyse the same reaction
different genetic parameters
ex: Lactate dehydrogenase
Multi-Enzyme Complexes
promote consecutive reactions: metabolic pathways
transit time via diffusions is reduced
less interference
Diagnostic Enzymology
Measurement of activity or concentration in serum
a lot of clinical exploitation
Serum Specific enzymes
normal locations : enzymes involved in blood coagulation
Secreted Enzymes
pancreatic
Non-serum specific enzymes
No physiological role in serum
- Released due to cell turnover, damage, morphological changes
