BCHM 100 Assignment 4 In class we have discussed how enzyme

| October 22, 2018

BCHM 100 Assignment 4In class we have discussed how enzyme assays can be used to determine the enzyme kineticconstants Vmax and Km but in this assignment you will do the reverse. You will use knownVmax and Km values to calculate expected rates for a pair of enzyme catalyzed reactions.Suppose that you are provided data about phenylalanine hydroxylase and phenylalanineaminotransferase (the enzyme that converts phenylalanine to phenylpyruvate in patients withPKU). You are told that the Vmax and Km values for phenylalanine hydroxylase in a standardenzyme assay are 100 µmol min-1 and 10 µM respectively, and those for phenylalanineaminotransferase are 10 µmol min-1 and 1000 µM respectively.Prepare a table that reports expected values of enzyme velocity (v) at the following substrateconcentrations ([s]): 1, 2, 6, 10, 20, 40, 60, 100, 500, 1000, 2400, 5000 (all values are in µM).Prepare Michaelis Menten plots that illustrate these kinetic data. Dont forget to carefully labelthe axes.Now consider this pseudo-clinical case of two patients with PKU. Assume that the production ofphenylpyruvate by phenylalanine aminotransferase at a rate of less than 1 µmol min-1 asmeasured by this assay can be handled by the body (the phenylpyruvate is converted tosomething non-toxic or is excreted) and does NOT cause PKU.A patient with mild PKU comes to the clinic with a blood phenylalanine concentration of500 µM. When his phenylalanine hydroxylase is assayed as described above, Vmax andKm values are found to be 100 µmol min-1 and 5000 µM respectively. Prepare aMichaelis Menten plot for his enzyme as described above using the same substrateconcentration range. To what extent has the change in Km affected his enzymes abilityto convert phenylalanine to tyrosine, assuming that the substrate concentration it seesis the same as the patients blood phenylalanine concentration? At this bloodconcentration of phenylalanine, at what rate is his phenylalanine aminotransferaseproducing phenylpyruvate? Is this rate consistent with a diagnosis of PKU (that is, is itabove 1 µmol min-1)?A patient with strong PKU comes to the clinic with a blood phenylalanine concentrationof 2400 µM. When her phenylalanine hydroxylase is assayed as described above, Vmaxand Km values are found to be 2 µmol min-1 and 10 µM respectively. Prepare a MichaelisMenten plot for her enzyme as described above using the same substrate concentrationrange. To what extent has the change in Vmax affected her enzymes ability to convertphenylalanine to tyrosine, assuming that the substrate concentration it sees is thesame as the patients blood phenylalanine concentration? At this blood concentration ofphenylalanine, at what rate is her phenylalanine aminotransferase producingphenylpyruvate? Is this rate consistent with a diagnosis of PKU that is more severe thanthe first patient?Complete the assignment and submit it to Michael Melesse (mmelesse@purdue.edu). Thishomework assignment is due by 11:59 p.m. Monday November 24, 2014. Late submissions willbe penalized at a rate of 5 points per day.

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