Question

This is a Biochemistry 200 level question, please answer neatly and as soon as possible. Thank you!

QUESTION 2 The kinetics parameters of several enzymes are listed below. Arrange the enzymes in order of decreasing catalytic efficiency. Enzyme Substrate kcat (s-1 Km Triosephosphate isomerase Glyceraldehyde-3-phosphate 4.3 x 103 0.47 mm Catalase H202 1.1 M Fumarase fumarate 5.0 x 10-6 M 4.0 x 107 8.0 x 102 5.7 x 103 1.0 x 106 Crotonase crotonyl-CoA 2.0 x 10-2 mm 1.2 x 10-2 M Carbonic anhydrase CO2 fumarase crotonase catalase triosephosphate isomerase carbonic anhydrase

Answer 1

table is given

now catalytic efficiency = kcat/Km.

So higher is the value of kcat/Km, greater will be catalytic activity.

For triosephosphate isomerase,

kcat = 4.3*10^3 /s

Km =0.47mM = 0.00047M

catalytic efficiency = kcat/Km = 4.3 * 10^(3) / 0.00047M

= 9.15 * 10^6

for catalase,

kcat = 4 * 10^7

Km = 1.1M

catalytic efficiency = 4*10^(7) /1.1 = 3.64 * 10^7

for fumerase, kcat = 8*10^2

Km =5*10^(-6)

catalytic efficiency = 8*10^(2) /5 *10^(-6)

= 1.6 * 10^8

for crotonase, kcat =5.7*10^3

Km =2*10^(-2)mM = 2 * 10^(-5) M

catalytic efficiency = 5.7*10^(3) / 2* 10^(-5)

= 2.85 *10^8

fo carbonic anhydrase

kcat =1*10^6

Km =1.2*10^(-2)M

catalytic efficiency = 10^(6) / 1.2 *10^(-2)

= 8.33 * 10^7

decreasing catalytic efgiciency

crotonase> fumerase >carbonic anhydrase>catalase>triosephosphate isomerase