Category: Enzymology

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Enzyme that would exhibit Michaelis–Menten kinetics

During an extended period of exercise, the enzymes involved in the glycolytic pathway in muscle tissue are actively breaking down glucose to provide the muscle energy. The liver, to maintain blood glucose levels, is synthesizing glucose via the gluconeogenic pathway. Which of the following enzymes involved in these pathways would be most likely to exhibit Michaelis–Menten kinetics, that is, have a hyperbolic curve when plotting substrate concentration versus velocity of the reaction? A) Fructose-1, 6-bisphosphatase B) Hexokinase C) Lactate dehydrogenase D) Phosphofructokinase-1 E) Pyruvate kinase The correct option is C- Lactate dehydrogenase. All the above mentioned enzymes are allosteric except...

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Aromatase inhibitor acting by increasing km value

Case details An 8-year-old girl presents with precocious puberty, short stature, and coffee-colored macules. The patient has been diagnosed with McCune-Albright syndrome that results from estrogen production due to excessive Aromatase activity from ovarian follicular cysts. To treat the precocious puberty and other symptoms, the patient has been prescribed with a drug that inhibits the Aromatase activity. The drug is known to act by binding to substrate binding site, producing an increase in km. Which of the following choices best describes the mechanism of inhibition of the drug? A. Competitive B. Non Competitive C. Allosteric D. Suicidal E. Feedback inhibition...

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Immediate treatment of Acute MI

Case details A 56-year-old man with hypercholesterolemia was rushed to the hospital with crushing chest pain radiating to his left arm and a probable heart attack. Which of the following treatments should be considered? A. A platelet transfusion B. Heparin transfusion C. Thrombin transfusion D. Fibrinogen infusion E. Tissue plasminogen activator infusion The correct answer is- E- Tissue plasminogen activator infusion. Tissue plasminogen activator (tPA) causes activation of plasminogen (zymogen form) to plasmin (active form). Plasmin hydrolyzes fibrin to form soluble degradation products (Figure-1). Figure-1- Mechanism of action of tPA The main goals of medical therapy of acute myocardial infarction...

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Significance of km

ENZYMOLOGY A teenager finishes eating a hot fudge sundae and a milk shake. As her blood sugar rises, the liver recruits both Glucokinase (km = 10.0m M) and Hexokinase (km = 0.10 mM) to metabolize the glucose. Which of the following is a correct statement about the kinetics of these two enzymes? A. Hexokinase will metabolize 100 times more glucose molecules B. Hexokinase will lower the energy of activation more than glucokinase C. Hexokinase has a much higher affinity to glucose than glucokinase D. Hexokinase will have a higher Vmax than glucokinase E. Hexokinase will be induced more than glucokinase...

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Case study- Enzymology- A teenager finishes eating a hot fudge sundae and a milk shake…

ENZYMOLOGY A teenager finishes eating a hot fudge sundae and a milk shake. As her blood sugar rises, the liver recruits both Glucokinase (km = 10.0m M) and Hexokinase (km = 0.10mM) to metabolize the glucose. Which of the following is a correct statement about the kinetics of these two enzymes? A. Hexokinase will metabolize 100 times more glucose molecules B. Hexokinase will lower the energy of activation more than glucokinase C. Hexokinase has a much higher affinity to glucose than glucokinase D. Hexokinase will have a higher Vmax than glucokinase E. Hexokinase will be induced more than glucokinase by...

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Case study- Enzyme Inhibition

A 54- year-old man complains of an acute onset of unilateral eye pain and reduction in the visual acuity. On physical examination, conjunctival injection (eye redness) and a mild-dilated and non reactive pupil is observed. Fundoscopic examination reveals cupping of the optic disc. Recognizing the signs and symptoms as glaucoma, the medication Acetazolamide is administered to decrease the production of aqueous fluid and lower the intraocular pressure. Acetazolamide is a non competitive inhibitor of carbonic anhydrase and therefore will cause: A. An increase in Km B. A decrease in Km C. An increase in Vmax D. A decrease in Vmax...

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Case study- Enzyme Inhibition- A 54-year-old man complains of an acute onset of unilateral eye pain and reduction in the visual acuity….

Basic concept Enzymes are catalysts of biological system. They speed up the rate of the reaction without themselves getting consumed during the process of catalysis. Active site is the place where the actual reaction between enzyme and substrate takes place. Coenzymes and cofactors are required by some of the enzymes to further accelerate the rate of enzyme catalyzed reaction. Many factors influence the rate of reaction including temperature, pH, substrate, enzyme and product concentration. Km denotes the affinity of the enzyme for its substrate, whereas Vmax signifies the maximum reaction velocity attained by enzyme catalyzed reaction. The enzyme activity can...

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