5 2. Peter does not tolerate lactose in milk. He bought a solution of B-galactosidase where[Eo] 10.0 µM. The concentration of lactose in milk is 150 mM and pH-6.3 Enzyme activitydepends on pH with constants: pka1-6.0, pka2=7.3 (the active form is partially protonated),KM-70 mm, kcat = 525 s¹ and enzyme loses half of its activity in 8 h. Find much enzymesolution (in mL) should Peter add to 1L of milk to reduce the concentration of lactose by80% after 10h to maximize the enzyme usage efficiency.

To determine the initial rate of reaction (Vo) Vo = Vmax [C]KM +[C]…

Answered: 2. Peter does not tolerate lactose in…

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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10. Chymotrypsin is a serine protease enzyme. The Km for the reaction of chymotrypsin with N-acetylvaline ethyl ester is 8.8*102, and the Km for the reaction of chymotrypsin with N- acetyltyrosine ethyl ester is 6.6*10“ M. catalytic triad Ser 195 His 57 Gly 193 N-H OH R-N- Ca N-H O-C- Asp 102 N-acetyl valine N-acetyl tyrosine Chymotrypsin Active Site a. What is the nucleophile here and how is it activated? b. Which substrate has an apparent higher affinity for the enzyme. c. Propose a reason for the difference in affinity based on the shape of each of the substrates (see active site figure, cleaves on the C-side of aromatic residues).
1. The optimal conditions for salivary lysozyme (hydrolyzing glycoproteins ofbacterial wall) are 37 C- temperature and pH is 5.2. Explain the decrease in this enzyme activity if the temperature will rise up to 60 °C and pH will be changed to 8.0. To answer the question: a) draw the graph of the velocity dependency on temperature and pH; b) calculate the relative enzyme activity if 10 mg of lysozyme catalyzes the formation of 5 uM of the product per 2 minutes. 2 Consider the matic reaction schee: Asnaragine + H20 Aspartate+ NH3:
We want to measure the activity of alanine aminotransferase (ALAT) present in a serum. The reaction catalyzed by the enzyme is: Reaction 1: I- *H₂N- glutamate H - C-COO CH₂ CH₂ COO 0.1 M phosphate buffer pH 7.4 : 550 μL 1.2 M alanine: 100 μL CH3 pyruvate CH3 C time (min) A340 CIO O COO The enzyme reaction is alized in the following conditions: In a 1 cm-cuvette are added: COO™ pyruvate lactate dehydrogenase* (LDH, 300 µμg.mL-¹): 50 μL 1.5 mM NADH : 200 μL 0.04 M a-ketoglutarate: 500 µL serum containing ALAT: 600 μµL ALAT NADH + H+ 0 0.915 a-cétoglutarate COO LDH * Lactate dehydrogenase (LDH) reduces pyruvate into lactate, with the concomitant oxydation of NADH. This allows to indirectly measure the amount of product formed. с=0 CH₂ 1 0.741 Reaction 2: NAD+ CH₂ COO™ H-C CH3 OH COO™ lactate alanine H + *H3N-C The reaction is performed at 25 °C and the absorbance at 340 nm is monitored every minute, for 5 min. The absorbance values are given in the table below: Data: ENADH at 340 nm =…
1. Penicillin is hydrolyzed and thereby rendered inactive penicillinase, an enzyme present in some penicillin-resistant bacteria. The molecular weight of this enzyme in Staphylococcus aureus is 29.6 kilo Daltons (29.6 kg/mole or 29,600 g/mole or 29,600 ng/nmole) The amount of penicillin hydrolyzed in 2 minute in a 10-mL solution containing 109 g (1 ng) of purified penicillinase was measured as a function of the concentration of penicillin. Assume that the concentration of penicillin does not change appreciably during the assay. [Hint: Convert everything to the same concentration terms] Show all calculations and include spreadsheets and graphs to determine Km, Vmax and kcat for this enzyme. Make sure your final answers have correct units. [Another hint: Note that [S] and amount hydrolyzed are already in concentration terms. So you don't need to worry about the volume for calculating [S] and V. ] Penicillin concentration (microM) Amount hydrolyzed (nanoM) 1 110 3 250 5 340 10 450 30 580…
1. You are working on an experiment with a newly discovered enzyme. This enzyme works most efficiently at a pH of 7.70. You make 250 mL of a 150 mM phosphate buffer, pH 7.70. (pK = 6.82). a. What are the concentrations of the weak acid and conjugate base forms of this phosphate buffer when you start the experiment? b. In the process of the enzyme catalyzed reaction, 25 mM acid (H+) is produced. What is the pH of the solution after the reaction is complete? Assume no change in volume by production of the acid. 2. Case Study Questions: Normal Levels of Substances in the Arterial Blood: PH 7.40 + 0.05 pCO2 (partial pressure of carbon dioxide) 40 mm Hg pO2 (partial pressure of oxygen) Hemoglobin - O₂ saturation [HCO3-] 90-100 mm Hg 94 - 100% 24 meq / liter A. Kim is a 38 year old woman admitted to the hospital for bulimia. Her laboratory results are as follows: pH 7.48, pCO₂ in the normal range and total HCO3 higher than normal. Classify her acid- base balance as acidosis or alkalosis and…
1. Calculate the pH of a 0.05 M solution of HCl. 2. Calculate the pH of a 0.1 M solution of NaOH. 3. Calculate the pH of an acetic acid solution in which [CH3COO - ] = 0.037 M and [CH3COOH] = 0.044 M. (pKa = 4.76) 4. You are conducting a biochemical experiment with an enzyme that has optimal activity at pH = 10.00. You decide to use carbonate (pKa1 = 6.38, pKa2 = 10.30) as the buffer to keep the pH stable throughout the enzymatic reaction. (Recall that the formula for carbonic acid is H2CO3.) You prepare a 0.5 M solution of carbonate buffer at pH = 10.00. Calculate the concentrations of the major carbonate species in your solution. 5. Calculate the pH of the buffer solution in which [H3PO4] = 0.038 M and [H2PO4 - ] = 0.046 M (pKa1 = 2.12, pKa2 = 7.21, pKa3 = 12.32). 6. Add 5.0 mL of 0.1 M NaOH to 80 mL of buffer from question 5 and calculate the pH.
The protein catalase is an enzyme that catalyzes the decomposition of hydrogen peroxide:2 H2O2 (aq) → 2 H2O (l) + O2 (g)and has a Michaelis-Menten constant of 25 × 10-3 mol·dm-3 and a turnover number of 4.0×107s-1.The total enzyme concentration is 0.016×10-6 mol·dm-3 and the initial substrate concentration is4.32×10-6 mol·dm-3 Calculate the maximum reaction rate (????) for this enzyme, and the initial rateof this reaction. Note that catalase has a single active site.
1. Acid phosphatases are an important group of enzymes that can be detected in human blood serum.Under slightly acidic conditions (pH 5.0), this group of enzymes can hydrolyze biological phosphate esters as follows: R-O-P-O3-2 + H 2O  R-OH + HO-P-O3-2. Acid phosphatases are produced and can be detected in erythrocytes, kidney, spleen, the liver, and prostate gland. The enzyme from the prostate gland is clinically important because an increased activity in the blood is frequently an indication of cancer of the prostate gland. Tartrate ion can strongly inhibit the phosphatase from the prostate gland, but not acid phosphatases from other tissues. How canyou use the information above to develop a specific procedure for measuring the activity of the acid phosphatase of the prostate gland in human blood serum?
5) In an experiment to investigate the inhibition of the enzyme-glucosidase the following data for the rates of reaction with glucopyranoside for various substrate concentrations was obtained. By constructing a Leaver-Burk plot, determine the value of the Michaelis constant. [S]/ (10-6 mol dm-3) v/ (10-3 mol dm-3 s-1) 1.00 2.00 3.00 4.00 16.7 33.3 41.1 49.8
We want to measure the activity of alanine aminotransferase (ALAT) present in a serum. The reaction catalyzed by the enzyme is: Reaction 1: +H3N- glutamate H C CH₂ CH₂ COO -COO + pyruvate CH3 C=0 0.1 M phosphate buffer pH 7.4 : 550 µL 1.2 M alanine : 100 μL CH3 time (min) A340 COO COO™ pyruvate lactate dehydrogenase* (LDH, 300 µg.mL-¹): 50 μL 1.5 mM NADH: 200 μL 0.04 M a-ketoglutarate: 500 μL serum containing ALAT: 600 μL The enzyme reaction is realized in the following conditions: In a 1 cm-cuvette are added: 0 0.915 ALAT NADH + H+ LDH a-cétoglutarate COO * Lactate dehydrogenase (LDH) reduces pyruvate into lactate, with the concomitant oxydation of NADH. This allows to indirectly measure the amount of product formed. Reaction 2: NAD+ 1 0.741 C=O H CH₂ CH₂ COO™ CH3 C-OH COO lactate The reaction is performed at 25 °C and the absorbance at 340 nm is monitored every minute, for 5 min. The absorbance values are given in the table below: Data: alanine ENADH at 340 nm = 6220 M¹.cm1. One…
A synthetic substrate, the para-nitrophenylacetate (PNPA), is used to monitor enzyme activity of protein P. The product of the hydrolysis reaction absorbs at 410 nm with a molar extinction coefficient of 4 000 M-¹.cm-¹. 1- Write the reaction catalyzed by the protease P using the pNPA substrate. 2- The enzyme extract is too concentrated and a 1/300 dilution is needed for enzyme tests. Considering that you would need at least 600 µL of diluted enzyme extract for activity tests, indicate which volume of buffer and enzyme extract you must use for the dilution.
5. For a Michaelis-Menten enzyme, k1 = 5.2 ⅹ 108 M-1 s-1, k-1 = 3.1 ⅹ 104 s-1, and k2 = 3.4 ⅹ 105 s-1. a) Write out the reaction, showing k1, k-1, and k2. Calculate Ks and Km. Does substrate binding approach equilibrium or the steady state? Justify your answer. b) What is kcat for this reaction? Justify your answer. c) Calculate Vmax for the enzyme. The total enzyme concentration is 25 pmol L-1, and each enzyme has two active sites. d) What substrate concentration would be required for the reaction in (c) to reach half of Vmax. Justify your answer mathematically. e) A second Michaelis-Menten enzyme has k1 = 4.2 ⅹ 107 M-1 s-1, k-1 = 6.1 ⅹ 104 s-1, and k2 = 5.3 ⅹ 102 s-1. Which enzyme is most efficient? 6. A pharmaceutical company is trying to develop a

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