A 32-year-old female presents to the clinic with complaints of fatigue, muscle weakness, and recurrent infections over the past few months. Laboratory tests reveal elevated levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in her blood, suggesting possible liver or muscle damage. Further investigation into her metabolic enzymes indicates a potential issue with an aminotransferase enzyme, which is known to catalyze a two-substrate, two-product (Bi-Bi) reaction. The medical team considers the enzyme kinetics involved to better understand the underlying mechanism and guide diagnostic and therapeutic decisions. Which of the following best describes the kinetic mechanism of the aminotransferase enzyme implicated in this patient’s condition?

A 42-year-old woman presents to the emergency department with symptoms of fatigue, nausea, and confusion. Laboratory tests reveal elevated ammonia levels, suggesting a defect in amino acid metabolism. Further testing indicates a deficiency in an enzyme that normally transfers an amino group from aspartate to α-ketoglutarate, forming glutamate and oxaloacetate. The enzyme follows a ping-pong Bi-Bi reaction mechanism. Which of the following best describes the enzymatic mechanism involved in this patient’s condition?

A new drug is being tested as an enzyme inhibitor. In a Lineweaver-Burk plot, the researcher notices that in the presence of the inhibitor: The y-intercept (1/Vmax) increases. The x-intercept (-1/Km) remains unchanged. What type of inhibition is most consistent with these findings?

A biochemist performs a Lineweaver-Burk analysis to determine the Km and Vmax of an enzyme. The resulting plot shows that the x-intercept is -1/5 mM⁻¹ and the y-intercept is 1/20 s. Which of the following represents the correct values of Km and Vmax?

A biochemistry researcher is studying an enzyme’s reaction kinetics. She generates a Michaelis-Menten curve and determines that at a substrate concentration of 5 mM, the enzyme operates at half its maximum velocity (Vmax/2). Which of the following best represents the Michaelis constant (Km) for this enzyme?

A 30-year-old athlete takes a high-protein diet to build muscle. His metabolism is highly active, requiring efficient enzyme function. The physician explains that enzyme activity follows Michaelis-Menten kinetics, with reaction rates dependent on substrate concentration. Which of the following best describes enzyme behavior as substrate concentration increases?

A 25-year-old medical student is preparing for an exam while consuming large amounts of coffee. He learns that pepsin, a stomach enzyme, functions at a very acidic pH (~2), while alkaline phosphatase operates in a basic pH (~9). Which of the following best explains the effect of pH on enzyme activity?

A 45-year-old man with bacterial sepsis presents with fever (39.5°C/103.1°F) and tachycardia. His metabolic panel reveals elevated lactate levels, suggesting increased anaerobic metabolism. The attending physician explains that enzyme-catalyzed reactions are affected by temperature. Which of the following best describes the effect of increased temperature on enzyme activity?

A scientist studying enzyme catalysis finds that, at equilibrium, the rate of substrate conversion to product is equal to the rate of product reconversion to substrate. Which of the following statements best describes the equilibrium state of this reaction?

A biochemist is studying enzyme kinetics and observes that doubling the concentration of reactant A results in a fourfold increase in reaction rate. Based on the rate law, what is the most likely order of the reaction with respect to A?