Question

Can anyone help with parts D and E?

Ibuprofen [a-methyl-4-(isobutyl)phenylacetic acid; Mr 206] reversibly inhibits cyclo-oxygenase (COX-2), a Michaelis enzyme that converts arachidonate to prostaglandin G2 (PPG2) thereby preventing the fever, inflammation and pain induced by prostaglandins. The following table shows a kinetic analysis of COX-2 in the absence and presence of 10 mg/ml Ibuprofen [Arachidonate] Vo mM/min w/o Ibuprofen Vo, mM/min w/ Ibuprofen mM 0.5 23.5 16.67 25.25 30.49 1.0 32.2 1.5 36.9 2.5 41.8 37.04 38.91 3.5 44.0 a. Make a fully labeled Lineweaver-Burk plot of the data (either manually or with a curve fitting program) and use it to determine Vmax, and Km for COX-2 and the apparent Vmax, and Km values in the presence of the Ibuprofen. b. What kind of inhibitor is Ibuprofen (viz., competitive, noncompetitive, uncompetitive)? Explain the basis of your assignment. What is the Ki for Ibuprofen with COX-2? c. d. COX-2 enzyme is a homodimer of Mr 140,000 with two active sites, and has a turnover number of 5.0 x 107 min-I under the assay conditions used to generate the data in the above table. How many grams of COX-2 per ml were present in the above assays? Calculate the efficiency value of this enzyme. Would you rate it a perfect enzyme? Explain. e.

Answer 1

Answer d:)

To quantify, grams/ml of an enzyme, we need to calculate enzyme concentration. We have been provided with Kcat value. We must know the Vmax value, which has been calculated in the part a. Therefore, calculate Enzyme concentration by using the following formula.

[E]₀ = Vmax /Kcat

After calculating Enzyme concentration use the following formula for finding the weight of the enzyme.

Grams/ml of Enzyme = Molecular weight in grams x 1000 / [E]₀

To convert molecular weight in grams, multiply the molecular weight with 10³ g/mol.

Here [E]₀ is in g/L because 1 Molar = 1g /L.

Answer e:)

To calculate, the efficiency of an enzyme, we calculate it through by finding the ratio of kcat/km. Higher than 1 value of Kcat/Km is related to the perfect enzyme category.

""""""""""""""Please rate the answer"""""""""""""""