The initial velocities of two different enzyme-catalyzed reactions were measured over a series of substrate concentrations. Thefollowing results were obtained:Enyme A: KM = 1.5 mM, Vmax = 10 μM s-1Enyme B: KM = 5.0 mM, Vmax = 85 µM s-1(a) Which enzyme binds to its substrate more tightly (assume k.1 >> k₂ in the Michaelis-Menten model)?(b) Calculate the initial velocities of each reaction when the substrate concentration is 2.5 mM.(c) Calculate the Kcat of each enzyme if the total enzyme concentration is 100 nM.(d) Which enzyme is the more efficient catalyst? Explain your answer.The enzyme carbonic anhydrase is strongly inhibited by the drug acetazolamide. A plot of the initial reaction velocity (as a percentageof Vmax) in the absence and presence of the inhibitor is shown below. What type of inhibition is taking place? Explain your reasoning.V (% of Vmax)100500.20.4No inhibitorAcetazolamide[S] (MM)0.60.81

Michaelis Menten postulated that free enzyme reacts with the substrate reversibly to form an…

Answered: The initial velocities of two different…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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You will perform the protocol below for the calf intestinal alkaline phosphatase (CIP) provided. For each reaction, your final enzyme concentration should be 10 nM CIP. Note: Enzymes purchased are typically labelled with their “units of activity” (U), as this relates to how much enzyme is needed to catalyze a reaction. The 100 nM CIP provided has approximately 3 U/mL and was diluted 1 in 1,000 from a 500 U/mL purchased enzyme. 1) Create a table (similar to the one below) to help you determine and keep track of what to add to each of the cuvettes in which your reactions will be measured. The five different concentrations of PNPP should be: 25, 50, 100, 200, 300 μM. Each reaction will be in a final volume of 1 mL and contain 10 nM alkaline phosphatase. Concentrations of stock solutions: 1.0 mM PNPP, 100 nM calf intestinal phosphatase
The protein catalase catalyzes the reaction 2H,O,(aq) — 2H,O(l) + O,(g) and has a Michaelis-Menten constant of KM = 25 mM and a turnover number of 4.0 × 107 s¯¹. The total enzyme concentration is 0.010 µM and the initial substrate concentration is 4.83 µM. Catalase has a single active site. Calculate the value of Rmax (often written as Vmax) for this enzyme. Rmax Calculate the initial rate, R (often written as V), of this reaction. R = ×10 mM.s-1 mM-s-1
The equil ibrium constant for the attachment of a substrate to the active site of an enzyme was measured as 200.In a separate experiment, the rate constant for the secondorder attachment was found to be 1.5 x 108 dm3 mol-1 s- 1.What is the rate constant for the loss of the unreacted substrate from the active site?
when saturated with substrate, an enzyme has a maximum initial rate of 110mumoles of substrate converted to product per second. At a substrate concentration of 100mu M, the same enzyme converts substrate to product at a rate of 0.010mmoles/ sec. Assuming that Michaelis - Menten kinetics are followed, calculate the reaction rate when substrate concentration is 2x10^-3M.
Consider an enzyme that follows standard Michaelis-Menten kinetics and has the following kinetic constants: %3| k2 = 1.5 x 10? s1 Еo 3D 1 х 104 М = 1 x 104 M a. What is the value of the maximum rate VM? b. Prepare a hand-drawn quantitative plot on graph paper (not a simple sketch nor an EXCEL-generated graph) of the enzymatic reaction rate versus substrate concentration (like Fig 3-3) using the kinetic parameters given above. Be sure to label the axes and include numeric values on the axes. C. Based upon your hand drawn saturation plot, at what substrate concentration is the enzymatic reaction rate 75% of Vm?
For an enzyme obeying the Michaelis-Menten equation with Km = 5 µM, kcat = 10 s-¹ and a total enzyme concentration of 1 nM, Calculate Vmax. Calculate the substrate concentration at which v = 0.1 Vmax Calculate the substrate concentration at which v = 0.9 Vmax What fraction of the enzyme is bound to substrate when v = 0.9 Vmax? Sketch a graph showing the Michaelis-Menten plot. Make sure you label the axes on your plot. Label on the graph: i) the point on the graph at which S=Km ii) Vmax At low substrate concentration, v = Keat [Etot] [S] Km Circle on your graph where this equation applies. What name is used to refer to keat/Km? : Calculate keat/Km for this enzyme. How does this value compare with the fastest enzymes?
Vmax and Km were calculated for enzyme substrate data. Results Y=0,0063x+0,3929 Km =62,4 mikromol/L Vm =159 mikromol/L.min But two additional data pairs were obtained at low concentrations and new graph equation Y=0,0063x+0,391 Recalculate Vmax and Km and compare and comment with previous results.
(b) You are investigating the effects of several agents on the activity of alcohol dehydrogenase. The enzyme activity data are shown in the table below. Construct a [substrate] vs. activity plot and a double-reciprocal plot for this enzyme. Be sure to label all axes. Determine the Vmax and KM for AD from the graphs in each type of plot. AD activity (nM/min) AD activity + agent A (nM/min) AD activity + agent B (nM/min) [Alcohol] (nM) 0.1 14 2 0.5 50 7 8. 1.0 65 10 30 2.0 72 12 45 4.0 80 14 62 8.0 85 15 75 32.0 90 16 90
An enzyme-catalyzed reaction is allowed to proceed for 3.4 minutes under steady-state conditions (with large excess of substrate). If the enzyme concentration is 7.9 nM, and the concentration of product formed is 6.3 µM, what is the kcat of this enzyme? Please give your answer to two significant figures in s1.
The effect of temperature on the hydrolysis of lactose by a ß-galactosidase is shown below in Table 1. The temperature coefficient, Q10 is the factor by which the rate increases by raising the temperature 10°C. The universal gas constant, R is 8.314 J/mol.K. (a) (b) Table 1: Data of Vmax over temperature T (°C) 20 30 35 40 45 Vmax (umoles/min.mg protein) 4.50 8.65 11.80 15.96 21.36 Plot the graph of In Vm vs 1/T using any spreadsheet software (include all appropriate labels and equation). Calculate the activation energy Ea and temperature coefficient Q10.
Study is being done where protein A isomerase (AI) is being phosphorylated by AI phosphorylase (AIP), at 37oC at physiological pH of approximately 7.4 with excess of Mg2+ and ATP. The Vmax and Km are determined to be 9 mM s-1 and 15 uM, respectively a) does AIP need any coenzymes, cofactors, co-substrates? b) what would be the formula for initial rate as a function of AI concentration? (Michaelis-Menten equation) c) what are the intial rates of reaction when [AI] = 3, 6 and 40 uM? Is the trend in initial rate vs [substrate] surprising? Explain.
Consider this intermediate in the derivation of the Michaelis-Menten equation. [E] [S] [ES| k-1 + kz km Assume that k is negligible compared to the other rate constants. If the k is very small, it suggests that the enzyme has a Select an option affinity for its substrate, while if the if the km is very large, it suggests that the enzyme has a Select an option. affinity for its substrate. Select an option Submit You have used 0 of high Sav low moderate

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