Introduces enzyme kinetics and defines Km and Vmax, including what a lower or higher Km signifies for substrate affinity. Covers the Michaelis-Menten equation and how substrate and enzyme concentration affect reaction velocity, then explains enzyme activity units (IU or U). Shows how the Lineweaver-Burk plot yields Vmax and Km from intercepts. Ends with two clinical applications: PRPP synthetase kinetics in gout and raised Km of acetaldehyde dehydrogenase causing ethanol sensitivity.
Topic 8 of 70 in the MU Sofia syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 7 sections, about 484 words (4 min of reading), with 10 flashcards.
In this note
Enzyme Kinetics
Definitions:
Michaelis-Menten Equation
Enzyme Units
Evaluation of Kinetic Parameters Vmax and Km via Lineweaver-Burk Plot
Kinetic Characteristics of Phosphoribosyl Pyrophosphate Synthetase in Cases of Gout
Increased Sensitivity to Ethanol Due to Increased Km of Acetaldehyde Dehydrogenase
Enzyme Kinetics
Enzyme kinetics is the study of the rates at which enzyme-catalyzed reactions occur and the factors that influence these rates. Understanding enzyme kinetics helps elucidate enzyme mechanisms and predict enzyme behaviour under various conditions.
Definitions:
Km definition: known as the Michaelis constant; is a key parameter in enzyme kinetics that describes the substrate concentration at which an enzyme achieves half of its maximum reaction velocity (Vmax). In other words, Km is the substrate concentration at which the rate of the enzyme-catalyzed reaction is half of its maximum rate.
A lower Km value indicates higher substrate affinity, meaning the enzyme can achieve half of its maximum velocity at lower substrate concentrations. Conversely, a higher Km value indicates lower substrate affinity, requiring higher substrate concentrations to reach half-maximal velocity.
Vmax definition: also known as the maximum reaction velocity, is another key parameter in enzyme kinetics. It represents the maximum rate of an enzyme-catalyzed reaction when the enzyme active sites are fully saturated with substrate.
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