Biochemistry

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Acetylcholinesterase catalyzes the hydrolysis of the neurotransmitter acetylcholine:

Acetylcholine + H2O  actetate + choline

The KM of acetylcholinesterase for its substrate acetylcholine is 9 x 10-5 M. In a reaction mixture containing 5 nanomoles/ml of acetylcholinesterase and 150 M acetylcholine, a velocity vo = 40 mol/ml –sec was observed for the acetylcholinesterase reaction.

Calculate Vmax for this amount of enzyme.

V_max=V_0 ([S]/([S]+K_M ))
V_max=40 μmol/min (((150 μM))/(150 μM+90 μM))=25 μmol/min





Calculate kcat for acetylcholinesterase.

k_cat=V_0/K_M [E][S]
k_cat=((40 μmol/min))/(90 μM) [150 μM][0.005 μmol/mL]=0.333


Calculate the catalytic efficiency (kcat/KM) for acetylcholinesterase.

k_cat/K_M =0.333/(9×〖10〗^(-5) )=0.0037

Does acetylcholinesterase approach “catalytic perfection”?

I'm not sure if I've done this right.

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