Questions and Answers
Enzyme kinetics studies the rates of enzyme-catalysed chemical reactions.
True
Enzymes are typically carbohydrates that promote a reaction of another molecule.
False
The enzyme-substrate complex is represented as ES.
True
The maximum rate an enzyme can achieve is unrelated to how easily it can be saturated with a substrate.
Signup and view all the answers
In enzyme kinetics, the transition state is represented as ES*.
Signup and view all the answers
Phosphoglucomutase is an example of a mutase.
Signup and view all the answers
Isomerases are commonly found in nature.
Signup and view all the answers
DNA polymerase links a nucleotide to DNA by joining two substrates.
Signup and view all the answers
Glyceraldehyde 3-phosphate dehydrogenase has two substrates and three products.
Signup and view all the answers
Proteases release multiple products from a single substrate.
Signup and view all the answers
Study Notes
Enzyme Kinetics
- Enzyme kinetics explores the rates of enzyme-catalyzed chemical reactions and the effects of varying reaction conditions.
- Understanding enzyme kinetics reveals the catalytic mechanisms, metabolic roles, activity control, and interactions with drugs or modifiers like inhibitors or activators.
- Two main properties assessed include substrate saturation levels and the maximum reaction rate achievable by the enzyme.
- Enzymes (E) bind substrates (S) at the active site, forming an enzyme-substrate complex (ES), which transitions to an enzyme-product complex (EP) before yielding the final product (P) via a transition state (ES*).
- Simple reactions typically involve one substrate and one product but are less common than more complex two-substrate, two-product reactions, such as those catalyzed by NAD-dependent dehydrogenases like alcohol dehydrogenase.
- Enzymes may also catalyze reactions with several substrates or products; for instance, glyceraldehyde 3-phosphate dehydrogenase involves three substrates and two products.
- Enzyme kinetics can illustrate the order of substrate binding and product release, especially in enzymes like dihydrofolate reductase.
- Advanced measurement techniques involve monitoring fluorescence changes, providing insights into individual enzyme kinetics rather than averaged behavior of large populations.
Allosteric Enzymes
- "Allosteric" is derived from Greek, meaning "other space," indicating regulation where binding at one site influences another spatially distinct site.
- Allosteric enzymes are regulated by noncovalent binding to effectors or modulators, impacting their catalytic activities and controlling metabolic pathways.
- Metabolic pathways consist of interconnected reactions, where enzymatic reactions' abundance and activity influence the overall metabolic flux, or turnover rate of metabolites.
- Effector binding can be either heterotropic (where binding of a small ligand alters substrate binding at a different site) or homotropic (binding of substrate influences its own binding affinity on another subunit).
- Positive cooperativity occurs when effector binding enhances substrate binding affinity, while negative cooperativity occurs when it impedes subsequent enzyme activity.
- Allosteric enzyme kinetics follow a sigmoid growth curve rather than the hyperbolic form associated with standard Michaelis-Menten kinetics.
Notable Allosteric Enzymes
-
Phosphofructokinase (PFK):
- Key regulator in the glycolysis pathway, converting fructose-6-phosphate (F6P) to pyruvate.
- Contains two active sites for F6P and ATP, along with a regulatory site for ATP or AMP.
- ATP serves as a negative effector and AMP as a positive effector, modulating PFK activity based on cellular energy levels.
- AMP stimulates glycolysis during low energy, while excess ATP inhibits it, diminishing enzyme affinity to F6P.
-
Isocitrate Dehydrogenase (IDH):
- Central to the citric acid cycle (Krebs cycle), essential for aerobic metabolism and biosynthesis of biomolecules.
- Exists as heterodimers with catalytic and regulatory subunits, integrated into a normal operational framework.
- Citric acid binds to the allosteric site, inducing conformational changes that facilitate substrate isocitrate binding and enzyme activation.
- High levels of adenosine diphosphate (ADP) enhance cycle rates through additional binding alongside magnesium ions (Mg²⁺), stabilizing substrate interactions without directly altering conformation.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Explore the fascinating field of enzyme kinetics, focusing on the rates of enzyme-catalyzed chemical reactions. This lecture note delves into how varying conditions affect reaction rates. Ideal for students and professionals looking to deepen their understanding of biochemistry.
