3. The enzyme -chymotrypsin is secreted in the pancreas of mammals and cleaves p

Question

3. The enzyme -chymotrypsin is secreted in the pancreas of mammals and cleaves peptide bonds between certain pairs of amino acids. The following table of data describes the initial rate (R) of at which the small peptide N glutaryl-L-phenylalanine-p-nitroanilide (the substrate, S) is consumed in the presence of a small amount -chymotrypsin. Using these data. determine the maximum rate Vmax and the Michaelis constant for the reactioin [S] (mML) 0.334 0450 0.667 1.00 1.33 1.67 R (mM/s) 0.152 0.201 0.269 0.417 0.505 0.667

Explanation / Answer

the max rate (Vmax ) and Michealis- Menten constant (KM)can be determined from

1/V= (KM/Vmax)*1/S + 1/Vmax

so a plot of 1/S vs 1/V gives straight line whose slope is KM/Vmax and intercept is 1/Vmax.

So a plot of 1/V vs 1/S will have to be generated. This is drawn in excel and shown below

from the equation of best fit from the plot, intercept is 1/Vmax= 0.3629, Vmax= 1/0.3629 mM/s =2.75 mM/s

slope is KM/Vmax= 2.093, KM= 2.093*2.75 mM=5.766 mM

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