Prostaglandins are lipid autacoids derived from arachidonic acid. They are essen

Question

Prostaglandins are lipid autacoids derived from arachidonic acid. They are essential for sustaining hemostatic function and play an important role in mediating pathogenic mechanisms - which include producing fever, inflammation and the accompanying pain associated with both of these immune responses. The biosynthesis of prostaglandins is as follows: Arachidonic acid, a 20-carbon unsaturated fatty acid, is released from the plasma membrane by phospholipases and metabolized by sequential actions of prostaglandin synthases. The enzyme prostaglandin endoperoxide synthase, a cydooxygenase, employs oxygen to convert arachidonic acid to PGG_2, an intermediate for a number of different prostaglandins. Kinetic data provided below is for this reaction. Determine V_max and K_m of prostaglandin endoperoxide synthase. (b) Ibuprofen, a known inhibitor of this enzyme, is commonly used to reduce pain resulting from inflammation. Using the provided kinetic data determine the type of inhibition and provide the V_max and K_m in the presence of ibuprofen. (c) Compare the values determined from parts a and b and explain these results.

Explanation / Answer

prostaglandin endoperoxide synthase. Kinetic data were also collected in the presence of ibuprofen, an inhibitor of prostaglandin endoperoxide synthase. Ibuprofen inhibits the synthesis of protaglandins, thus aiding in reducing inflammation and pain. The data collected in the presence of ibuprofen are given in column 1 & 3. Analyze the data using a Lineweaver-Burke plot. What is the Vmax and Km of the enzyme in the absence of ibuprofen? What kind of inhibitor is ibuprofen?

+1 for use of Lineweaver-Burke plot.

+1 for Vmax value

+1 for Vmax units

+1 for Km value

+1 for Km units.

+2 for type of inhibition

Vmax = 51.55 mM/min---answer

; Km = 0.598 mM;---answer

ibuprofen is a competitive inhibitor. Can't determine it directly because we can never truly reach Vmax.

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