tim triose phosphate isomerase Flashcards
Tim do not stabilise the
enzyme substrate complex
boltzmann distribution
with catalyst, Ea is reduced so more Particles can over come Ts
some particles decompose into products
what is Tim involved in
glycolysis
DHAP - G3P
no regulation, needs to be as fast as possible
redox reaction needed
why is a redox reaction needed
because we cant move H from C1 to C2 in 1 step
what happens in hindsight
4 points
base attacks C1 hydrogen and
oxygen on C2 takes H+ off an acid
another base then attacks OH on C1 while
the double bond formed between C1 and 2 attack acid and take proton forming G3P
what AA are used in tim
Glu 165
His 95
specific acid/base catalysis
proton transfer occurs prior to bond - cleavage
general acid/base catalysis
proton transfer is a characteristic of the transitional state
TIMs structure
(beta alpha)8 barrel
motif 8 times repeated
beta followed by alpha
parallel
TIMs transition states general features
several transition states
free energy of E+DHAP is lower then E+G3P
they are at equilibrium but G3P is tapped off
4% is enough for this equilibrium to happen
there is a large what
excess of reactant over product
which compensates for the slow rate
if cat added ratio will not change but the rate will increase in both directions
TIM transition states what are they though to have
similar energy barriers
highest energy barrier is TS4
this is product release which is close to diffusion controlled rates
where is the active site
always on the C-terminal side (arrowhead)
inserts between beta strands
mostly c-terminal
convergent evolution
different functions converging into the same fold
divergent evolution
common ancestor structure diverges into different functions
