Enzymes Flashcards

Enzymes

Primarily globular proteins (or ribozymes) that act as catalysts to accelerate chemical reactions within living organisms

Cofactors

Additional non-protein components required for enzyme activity

Specificity

Each enzyme is tailored to target a specific substrate or group of substrates

Reusability

Enzymes are not consumed in reactions, allowing multiple reaction cycles

Active Site

Specialized region where substrate binding occurs and the chemical reaction unfolds

Catalysis

Enzymes lower the activation energy threshold, making reactions occur more readily

Ribozymes

RNA molecules that catalyze biochemical reactions such as RNA splicing, RNA cleavage, and peptide bond formation

Coenzyme (cofactor)

Non-protein organic or metallorganic molecules loosely attached to enzymes

Prosthetic Group (cofactor)

Non-protein organic molecules tightly or covalently attached to enzymes

Metal-Ion Activators (cofactor)

Essential metal ions (e.g., Mg²⁺, Zn²⁺)

Oxidoreductases

Facilitate redox reactions

Transferases

Transfer functional groups between molecules

Hydrolases

Conduct hydrolysis reactions, breaking chemical bonds with water

Lyases

Break chemical bonds without water or oxidation

Isomerases

Catalyze the rearrangement of atoms to form isomers

Ligases

Join two molecules together using ATP/GTP for energy

Translocases

Facilitate movement of molecules across membranes

Absolute Specificity

Enzymes catalyze only one specific reaction

Group Specificity

Enzymes act on specific functional groups

Linkage Specificity

Enzymes target specific types of chemical bonds

Stereochemical Specificity

Enzymes act on a particular steric or optical isomer

Active Site

Specialized region in the enzyme where substrate molecules bind and react

Hydrogen Bonds

Weak interactions helping in substrate binding

Ionic Interactions

Charge-based interactions stabilizing substrate binding

Van der Waals Forces

Weak molecular forces stabilizing enzyme-substrate complex

Hydrophobic Interactions

Nonpolar interactions in some enzymes

Lock-and-Key Model

Rigid active site that precisely fits the substrate

Induced Fit Model

Active site undergoes conformational change upon substrate binding, enhancing interaction

Spontaneous Reactions

ΔG < 0

Non-Spontaneous Reactions

ΔG > 0

Michaelis-Menten Kinetics

Relationship between enzyme concentration, substrate concentration, and reaction rate

KM Value

Binding affinity of enzyme for its substrate (lower KM = stronger affinity)

Vmax

Maximum reaction rate at full substrate saturation

Homotropic Regulation

The substrate itself acts as the regulatory molecule

Heterotropic Regulation

A different molecule regulates enzyme activity by binding to an allosteric site

Positive Cooperativity

Binding of first molecule increases enzyme affinity for additional molecules, producing a sigmoidal kinetic curve

Negative Cooperativity

Binding of first molecule decreases enzyme affinity for additional molecules, leading to a flattened kinetic curve

Competitive Inhibition

Inhibitor competes with substrate for the active site (KM increases, Vmax constant)

Non-Competitive Inhibition

Inhibitor binds to an allosteric site, altering enzyme shape (KM constant, Vmax decreases)

Uncompetitive Inhibition

Inhibitor binds to enzyme-substrate complex, preventing product formation (KM and Vmax decrease)

K-type Allosteric Enzymes

Effectors modify enzyme affinity for the substrate, altering KM

Positive Effectors

Decrease KM (higher affinity), shifting sigmoidal curve left

Negative Effectors

Increase KM (lower affinity), shifting sigmoidal curve right

V-type Allosteric Enzymes

Effectors influence enzyme Vmax

Positive Effectors

Increase Vmax, boosting catalytic efficiency

Negative Effectors

Decrease Vmax, reducing catalytic efficiency

Optimal Temperature

Enzyme activity increases up to an optimal temperature (often ~37°C for human enzymes) before denaturation

Optimal pH

Each enzyme has a preferred pH range (typically pH 6-8), outside of which activity decreases

Salinity Effects

High salt concentrations can disrupt ionic bonds and alter enzyme structure, reducing activity

Enzyme Immobilization

Attaching enzymes to solid supports or confining them within matrices while maintaining their activity in bioprocesses

Adsorption

Enzymes bind non-covalently to support material

Covalent Bonding

Enzymes attach covalently to support materials

Encapsulation

Enzymes are enclosed in semipermeable material

Entrapment

Enzymes are physically trapped within a porous matrix

Cross-Linking

Enzymes are linked to each other using cross-linking agents

Gold-Thiol Conjugation

Covalent attachment of thiol-containing molecules (e.g., enzymes, proteins) to gold surfaces via strong thiol-gold bonds

NHS/EDC Reaction

Bioconjugation method forming amide bonds between carboxyl (-COOH) and amine (-NH2) groups

7 major enzyme classes

oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases, translocases

Hill coefficient (n)

describes the degree of cooperativity in multimeric enzymes

Concerted model

explains how initial substrate binding to a multimeric enzyme influence subsequent affinity for the substrate

Sequential model

explains how ligand binding to a multimeric enzyme or protein influence the affinity of neighboring subunits