9.Effect of pH and Temperature on Enzyme-Catalyzed Reactions
Covers how temperature and pH change enzyme velocity, from the rise to an optimum to denaturation at extremes, with pepsin and alcohol dehydrogenase given as examples of pH sensitivity. It then reviews regulation by allosteric binding, covalent modification, proteolytic cleavage, feedback inhibition and substrate availability, followed by competitive and non-competitive inhibitors, antimetabolites such as methotrexate, and orotic aciduria with its causes, symptoms and treatment. Several diagrams and a short multiple-choice set with answers are included.
Topic 9 of 70 in the MU Sofia syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 16 sections, about 939 words (7 min of reading), with 10 flashcards.
In this note
Effect of pH and Temperature on Enzyme-Catalyzed Reactions
Regulation of Enzyme Activity
Inhibition Mechanisms
Allosteric Regulation Overview
Types of Allosteric Regulation
Antimetabolites Overview
Goat in GPAT Allosteric Center Defects
Orotaturia Overview
OROTIC ACIDURIA
osms.it/orotic-aciduria
PATHOLOGY & CAUSES
SIGNS & SYMPTOMS
DIAGNOSIS
TREATMENT
MCQ ☺
Answers
Effect of pH and Temperature on Enzyme-Catalyzed Reactions
Temperature
Increase of velocity with temperature:
Increases until a peak is reached.
Increased number of molecules have sufficient energy to overcome the energy barrier and form reaction products.
Decrease of velocity at higher temperatures:
Temperature-induced denaturation of the enzyme.
The optimum temperature for most human enzymes is 35 to 40 degrees Celsius, beyond which they denature.
pH
Effect of pH on the ionization of the active site:
The active site's amino acid residues can exist in different ionization states depending on the pH, affecting substrate binding and catalysis.
Enzyme stability and activity are influenced by pH, with optimal ranges for maximum activity.
Effect of pH on enzyme denaturation:
Extremely high or low pH levels can denature enzymes, altering their structure and function.
Optimum pH varies for different enzymes:
Each enzyme has a specific pH range for optimal activity; for example, pepsin operates best at pH 2.
Changes in pH optimum due to high ethanol sensitivity:
In high ethanol sensitivity, the pH optimum for alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) can shift, affecting ethanol metabolism.
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