4. I would like you to design a process for producing the amino acid threonine (C4H9O3N; MW-119.1) using E. coli cells (CH1.800.5 No.2). Your carbon and nitrogen sources will be glycerol (C3H8O3, MW =92) and ammonia (NH3), respectively. Small-scale experiments showed that we can achieve the following cell and product yields: Yxs = 0.2 g cell/g glycerol, YP/S 0.15 g threonine/g glycerol. a. (15 pts) Assuming that cell growth and threonine production occurred simultaneously, write a balanced stoichiometric reaction for this biological process. (92% of the E. coli dry cell weight is composed of C, H, O, and N. Their atomic masses are 12, 1, 16 and 14, respectively.) b. (4 pts) What is the product yield on cells (YPX; g threonine/g cell)? c. (3 pts) Two other mutated strains of E. coli have YP/S = 0.28 g threonine/g glycerol and YP/S = 0.05 g threonine/g glycerol, respectively. When you compare these mutated strains, d you replace it with any

5) The disease Phenylketonuria (or PKU) occurs when the enzyme that helps to catalyze the conversion of the amino acid phenylalanine into non-harmful tyrosine is mutated and doesn't work as well (or at all). Phenylalanine will still break down into tyrosine by itself, because this is a favorable reaction. Why is the non-functional enzyme a problem? Explain in a few sentences. al.H.colbe91srtihot wolsd sldu non lom i anolterineon mundillups betsmus 8880

The purified OXA-M290 enzyme can now be tested to determine which β-lactamase inhibitor is most effective. This inhibitor could be prescribed in combination with a β-lactam antibiotic to treat the infection caused by the E. coli KGH1 strain. Before testing inhibitors against OXA-M290, the kinetic activity of this enzyme must first be measured. The activity of OXA-M290 is measured using nitrocefin, a chromogenic β-lactam antibiotic. When nitrocefin is hydrolyzed by a β-lactamase, it changes from yellow to red in colour. The nitrocefin hydrolysis product has an extinction coefficient of 20,500 M-1 cm-1 at 486 nm. The hydrolysis of 60 μM nitrocefin by 1 nM OXA-M290 is monitored using a microplate reader. The absorbance of the wells in the plate is measured at 486 nm every 30 seconds. This experiment is carried out with three replicates, generating the following data: Time (min) Absorbance of Replicate 1 Absorbance of Replicate 2 Absorbance of Replicate 3 0.5 0.0984…

Using the appropriate graph and table above, explain what the R48C mutation appears to be doing to the enzyme’s function.  Discuss the kinetic parameter changes and their meaning in this context, not the structure of the enzyme, which was not given to you.

Match the following catalytic strategies with their example. Place a Letter on the picture. There are only two examples given. CH2OH CH2OH CH2OH CH2OH он он OH OH + H20 OH OH OH но H. но но OH OH OH OH OH OH A. Oxidoreducatase B. Transferase C. Hydrolase D. Lyase NH3 E. Isomerase F. Ligase R-CH-COO "ooc-CH2-CH2-C-COO Amino acid a-Ketoglutarate

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 =…

4. Below is a Michaelis-Menten plot for a wild-type (WT) and mutant (V105A) enzyme isolated from the bacterium Staphylococcus aureus. The enzyme is involved in carbohydrate metabolism and is a potential biocatalyst for the large-scale production of rare sugars. (8) mg V₂ μmol s1 1.50- 1.25- 1.00- 0.75- 0.50- 0.25- 0.00 0 100 200 300 [s], mM 400 500 WT (a) Estimate the KM and Vmax for the wild-type and mutant enzyme from the graph. V105A (b) Calculate the keat and keat/KM for the wild-type and mutant enzyme based on your estimated values in (a) if the total enzyme concentration is 0.5 µmol/mg. (c) Is the mutant enzyme a more or less efficient catalyst than the wild-type enzyme? Briefly explain.

3. Below is a Michaelis-Menten plot for a wild-type (WT) and mutant (V105A) enzyme isolated from the bacterium Staphylococcus aureus. The enzyme is involved in carbohydrate metabolism and is a potential biocatalyst for the large-scale production of rare sugars. -1 v, μmol s¹ mg-¹ 1.50- 1.25- 1.00- 0.75- 0.50- 0.25- 0.00+ 0 100 → WT 200 300 [s], mM 400 500 → V105A (a) Estimate the Km and Vmax for the wild-type and mutant enzyme from the graph. (b) Calculate the Keat and Keat/Km for the wild-type and mutant enzyme based on your estimated values in (a) if the total enzyme concentration is 0.5 µmol/mg. (c) Is the mutant enzyme a more or less efficient catalyst than the wild-type enzyme? Briefly explain.

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

Cysteine proteases are enzymes that degrade proteins. You may have heard of some examples of these types of proteins before! Bromelain is an enzyme found in pineapple that is commonly used as a meat tenderizer and is the reason Jell-O with fresh pineapple will not solidify. Cysteine proteases are remarkably similar to serine proteases (like chymotrypsin), except they have a cysteine in their active site rather than a serine. Using the mechanism that we discussed for serine proteases, draw a corresponding mechanism for a cysteine protease cleaving the bond between an alanine-glycine dipeptide. Note that cysteine proteases do not require an aspartate in their active site. Also note that the cysteine is usually in its thiolate form (deprotonated) and the histidine is in its imidazolium form (fully protonated) in the resting state of the enzyme.